Biodegradable, Industrially Compostable, and Recyclable Injection Molded Microcellular Flexible Foams

ABSTRACT

This document discloses a process for manufacturing recyclable injection molded microcellular foams for use in, footwear components, seating components, protective gear components, and watersport accessories. The process includes the steps of providing a thermoplastic polymer which comprises at least one monomer derived from depolymerized post-consumer plastic, inserting a fluid into a barrel of a molding apparatus. The fluid is introduced under temperature and pressure conditions to produce a super critical fluid. The process further includes mixing the thermoplastic polymer and super critical fluid so as to create a single phase solution, and injecting the single phase solution into a mold of an injection molding machine under gas counter pressure. The process further includes foaming the single phase solution by controlling the head and temperature conditions within the mold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 62/853,805, entitled “RECYCLABLE ANDCHEMICAL-FREE INJECTION MOLDED MICROCELLULAR FLEXIBLE FOAMS, AND AMETHOD OF MANUFACTURING THE SAME,” and filed on May 29, 2019, and is acontinuation-in-part of patent application Ser. No. 16/418,968, filedMay 21, 2019 entitled “BIODEGRADABLE AND INDUSTRIALLY COMPOSTABLEINJECTION MOLDED MICROCELLULAR FLEXIBLE FOAMS, AND A METHOD OFMANUFACTURING THE SAME,” which claims priority to and the benefit ofU.S. Provisional Patent Application No. 62/674,544, entitled“BIODEGRADABLE AND INDUSTRIALLY COMPOSTABLE INJECTION MOLDEDMICROCELLULAR FLEXIBLE FOAMS, AND A METHOD OF MANUFACTURING THE SAME,”and filed on May 21, 2018, the disclosures of which are all incorporatedherein by reference in their entirety for all purposes.

BACKGROUND

The present disclosure relates to a process for injection moldedmicrocellular foaming various flexible foam compositions from recyclableor biodegradable, industrially compostable bio-derived thermoplasticpolymers for use in, for example, footwear components, seatingcomponents, protective gear components, and watersport accessories.

Degradation through composting is an important process for renewingresources used in producing manufactured goods. However, when thosemanufactured goods involve foam, decomposition may be problematic.Particularly, there are several disadvantages of conventionally knownmethods of flexible foam manufacturing. For instance, such disadvantagesinclude the selection and use of non-renewable polymers, chemicalblowing agents, and chemical additives, which as employed in the foammanufacturing industry and the processing procedures inherent, do nottypically biodegrade, and that are generally considered bad for theenvironment. This lack of biodegradation means that many conventionalflexible foam materials and the products with which they are contained,end up in landfills for anywhere from decades to centuries.

This is also problematic because the overuse of landfills in the worldtoday has a direct negative impact on both the environment and theeconomy. For example, landfills are the third largest source of methaneemissions in the United States. Further, the aforementionednon-biodegradable polymers and chemicals used in convention flexiblefoams are particularly derived from non-renewable resources.

These materials are not naturally renewable, as is the case withbio-derived feedstocks, and therefore, their very creation is a net lossfor the environment as their materials are often taken, used, and thendiscarded non-sustainably. Furthermore, even if renewable polymers wereselected for use in conventionally known method of flexible foammanufacturing, the chemical blowing agents and crosslinking of thosemethods would likely contaminate the renewable polymer with additivesthat do not biodegrade or compost. Thus, making it a zero-sum gain.Further still, the crosslinking of the biopolymer would also likelyprevent any suitable end-of-life solution for biodegrading or compostingas the precursor components could not be separated thereby resulting inmore waste generation and more material going to landfill.

Accordingly, although composting and recycling are important process inproviding for a renewable and sustainable future, its integration in themanufacturing industry is very limited. However, it would be veryuseful, e.g., to the environment, if manufactured materials could bemade compostable. For instance, the composting and biodegradation offlexible foam materials creates an opportunity of waste disposal thatrepresents a net-benefit to the environment and the economy. Forexample, by composting these materials, it would make it possible toreduce the overall amount of waste being sent to landfills and mass-burnincinerators.

In addition to reducing waste, the process of composting would alsocreate a usable product that is nutrient-rich and could be used to amendpoor soils to grow food or to fertilize gardens. Accordingly, the verynotion of composting and biodegrading flexible foams, however novel, canrevolutionize the entire value chain while keeping to the principals ofthe so-called circular economy. There are two typical forms ofcomposting: industrial composting and home composting. Both of thesecomposing methodologies have benefits and drawbacks.

Industrial composting is a form of large-scale composting that isdesigned to handle a very high volume of organic waste. It is conductedin large-scale facilities at temperatures between 50° to 60° C. Homecomposting is a form of composting that handles organic waste from onehousehold. Particularly, home composting refers to composting atrelatively lower temperatures, like those found in a backyard compostheap at home, hence the title “home”. In contrast to industrialcomposting, home composting involves a cooler aerobic breakdown oforganic material or waste such as yard trimmings, kitchen scraps, woodshavings, cardboard, and paper. The volumes treated in home compostingare considerably smaller than in industrial composting and the compostis usually used in private gardens. This process is typically conductedin small-scale composters and heaps. In this method, temperatures aretypically in the psychrophilic (0-20° C.) to mesophilic (20-45° C.)ranges (explained below). Accordingly, different technologies exist, butthe general processing is the same: a controlled process of activecomposting followed by curing.

The active composting phase typically lasts at least 21 days. Underthese conditions, microorganisms grow on organic waste, breaking it downto CO2 and water, using it as a nutrient. During composting, organicwaste is amassed in piles and, as a result, part of the energy ofcomposting is released as heat. When the temperature of the compostingpile increases the microbial populations shift: microbes adapted toambient temperature, e.g., mesophiles, stop their activity, die-off, andare replaced by microbes adapted to live at high temperature, e.g.,thermophiles. For hygienisation purposes, for home composting,temperatures should be maintained above 60° C. for at least a week, inorder to eliminate pathogenic microorganisms. By contrast, the curingphase of industrial composting slows the rate of decomposition to aconsistent pace, and the compost matures at temperatures in the lowermesophilic range of below 40° C.

A primary problem with industrial composting is that the inputfeedstocks should be disposed appropriately in order to be effectivelyprocessed. That is, the logistical challenges are a hurdle in thatproper collecting, sorting, and transporting to an industrial compostingfacility is required. The combined composting and recycling diversionrate of the United States is around 35%, which indicates that societyhas a long way to go before the vast majority of infrastructure is“closing the loop” on waste diversion. One method of overcoming thisshortfall is to better educate the end-user and to establish a localizednetwork of take-back schemes that feed into larger take-back schemes.The goal being to develop enough of a convenience and accessibility thatindustrial composting becomes normalized and ever-present in daily life.

Likewise, a prevalent disadvantage in home composting is the amount ofeffort involved. All of the required compost-feedstock materials need tobe carried and/or transferred to the compost pile. Once the compost heapis large enough to begin generating energy, and thereby heat, it needsto be turned to make the decomposition faster and more thorough, whichcan be strenuous work. When the organic matter is sufficientlydecomposed, the home compost must be hauled away for use in soilamendment. Another drawback of home composting is the limited quantityof useable compost that the average person can generate in ahome-setting. The limited amount of generated compost potentially givesway to limited use, and thus, the motivation of the average person tocommit to the effort of home composting can be low.

Because of these drawbacks, traditionally, the manufacturing industryhas avoided the use of raw materials and precursor ingredients with thepotential to biodegrade or compost. Additionally, this has traditionallybeen avoided because the required technical performance properties ofthese materials were often inferior to that of the conventionalnon-biodegradable and non-compostable variety. For instance, a limitingfactor of some, but not all, compostable precursor ingredients can bethe tendency for these ingredients to breakdown and/or degrade beforethe end of the product's useable life. An example of this would be anultra-violet sensitive product whereby the biodegradable and compostableprecursor might be attacked and weakened by repeated sunlight exposurewhich might eventually lead to the products failure well before theend-user was ready to dispose of the product.

In the context of plastics, thermoplastics and other products createdusing fossil fuels, recycling conventionally involves mechanicallyshredding a manufactured product, melting the shredded contents, andthen pelletizing the resulting material for later use in manufacturing.Although recycling reduces the need for fossil fuels and divertsproducts from landfills, recycling may result in a loss of quality inthe recycled polymers as a result of contamination or impurities addedto the feedstock, and most plastic and thermoplastic products can onlybe recycled a finite number of times. Moreover, the chemical blowingagents, crosslinked polymers, and chemical additives used in themanufacture of conventional flexible foam results in end products thatcannot be broken down into their constituent polymers for later use inmanufacturing a recycled product. Consequently, conventionallymanufactured flexible foam products are not recyclable when the producthas reached the end of its usable life.

Additionally, a current concern for modern manufacturing is beingnet-neutral with respect to emissions and waste, sustainable withrespect to materials being used in the manufacturing process, andrenewable with respect to the end of life of the product and itsmaterials. So being, net-neutrality, such as with respect to CO₂emission, In addition to compostability of the end product has becomeimportant in choosing the appropriate materials for use in manufacturingof consumer goods products.

Consequently, it is a key driver for the present manufacturing processesdisclosed herein, as compared to the more traditional manufacturingprocesses currently present, is that manufacturers produceenvironmentally-thoughtful end products, and so being, it is useful tocarefully consider the materials used in the manufacture of said endproducts, and to balance that against the intended useable-life of theproduct. An example of challenging products during the production ofwhich these concerns should be, but are not, addressed are standardmanufactured products employing foam, such as in the production ofcushioning, such as for furniture, and/or foam products, such as for themanufacture of running shoes.

For instance, running shoes are a highly technical product that areexposed to repeated abuses, such as: impact, abrasion, and all manner ofenvironmental exposures over considerable amounts of time; perhaps 1-3years depending on the frequency of use. When considering sustainablematerials for the use in manufacturing cushioning for furniture or forsoles, mid-soles, and/or cushioning for insoles of running shoes, it isimportant to take the above requirements into account. A material thatcannot handle repeated abuse before failure would not produce asatisfactory pair of running shoes. Additionally, any material that hasthe potential to break-down or weaken to the point of failure duringregular product use, prior to the intended end-of-life, would not beacceptable.

SUMMARY

In order to solve this problem, one must seek-out specialized materialswith the right balance of technical performance properties, andsustainability aspects, such as compostability with a managedend-of-life solution, that is net-neutral (or negative) with respect toharmful emissions. Particularly, since furniture cushioning is bulky andrunning shoes are a demanding product, home composting materials wouldnot be a suitable solution for use in their making as the lowerbreak-down temperatures would translate to furniture or a running shoethat would be prone to falling apart long before its intendedend-of-life. In this example, materials that industrial compost are amuch better option as they can handle higher temperature challenges andoffer greater technical performance properties near equal to or equal totheir non-industrially compostable and non-biodegradable counterparts.Essentially, furniture or a pair of running shoes manufactured withindustrially compostable materials would function very well for theuseable life of the product, and only at the end of the products useablelife would the materials have the option to be directed into industrialcompost settings for “closed loop” waste diversion.

Accordingly, where possible, in order to reduce the destructivefootprint often attendant to the manufacturing process, the materialsand processes of manufacturing should be formulated in such a mannerthat allows for ready composting after the end of the life of theproduct. However, as indicated above, this is difficult because thereare very limited biodegradable and compostable precursors commerciallyavailable. Those that do exist are not necessarily designed and capableof solving all of the combined challenges of performance and long-termusability while readily composting and biodegrading in a controlledsetting at the end of their useable life. Those precursors that solvesome of the aforementioned challenges, fail to solve others and thisleads to the potential of consternation in the consumer and likely badreviews of the products within which they are contained. Despite thesesignificant drawbacks, materials that can compost either at anindustrial facility or at home would theoretically be useful startingproducts in renewable, sustainable, and green manufacturing.

Another aspect of present manufacturing processes is with respect to theproduction of flexible foams. Flexible foams are a type of object formedby trapping pockets of gas in a liquid or solid whereby the resultingfoam is said to be flexible due in part to its malleability. Flexiblefoams are typically used in cushioning applications, such as footwear,furniture, bedding, and other sporting goods. Flexible foams typicallyfall into two categories: closed-cell flexible thermoplastic polymerfoams and open-cell flexible polyurethane foams. Each of these foamtypes have very different manufacturing methods.

Closed-cell flexible thermoplastic polymer foams are commonly producedin a dry process in which a suitable man-made polymer is selected andblended with various chemical additives, crosslinking agent, andchemical blowing agent for producing a “dough,” which dough is thenkneaded and extruded into flat sheets. The sheets are then stacked ontop of each other and placed in a heated press under controlledpressure. This mixture of materials and the chemical blowing agent reactand expand inside of the heated press cavity. The result is aclosed-cell flexible foam “bun” or “block” that is then sliced tothickness. By contrast, open-cell flexible polyurethane foams arecommonly produced in a liquid pouring process or liquid molding processin which a man-made polyol chemical, isocyanate chemical, and otherchemical additives, are reacted together while being poured or injectedinto a molded shape, such as a “bun” or “block”. The result is anopen-cell flexible foam that is then sliced to thickness.

Consistent with the above, one of the problems with the presentlyavailable flexible foams in the market today is that they almostexclusively use non-renewable materials, and harmful chemicals in theirmanufacture. Furthermore, due in part to the chemical-crosslinking thattakes place in the above described methods of manufacturing theconventional flexible foams, the physical structure of those flexiblefoams cannot be composted, biodegraded, or recycled. This is due inlarge part to the chemical compositions of their design and theirinability to be separated back into their root precursor constituents.That is, at the end of the conventional flexible foams life it has nofurther use and cannot be reprocessed into new material successfully inany known commercially viable methods.

Accordingly, in view of the above, presented herein are flexible foamsand manufacturing processes that may be employed to produce end productsthat are renewable, sustainable, and/or environmentally accountable,which materials and end products are capable of both sustained use,without breakdown, but rapidly degrade and compost after end of life.Both flexible and semi-flexible foams can be included under the samecategory of flexible foams as they both are derived from polymers with aglass transition (Tg) below their service temperature, which is usuallyat room temperature. The details of one or more embodiments are setforth in the accompanying description below and with respect to thepresented figures and their features. Other features and advantages willbe apparent both from the description, figures, and from the claims.

This document presents a process for modified injection moldmicrocellular foaming various flexible foam compositions frombiodegradable and industrially compostable thermoplastic resins.Presently, almost all known flexible foams in the world are derived fromnon-renewable feedstocks, and most, if not all, do not biodegrade orindustrially compost. It is an object of this invention to produceflexible foams that cause the least amount of environmental harm, butthat also boast significant technical performance properties equal orgreater than that of conventional non-biodegradable petrochemicalflexible foams. By selecting plant-derived feedstocks for producingbiopolymers, this invention contributes to sequestering greenhouse gasesfrom the atmosphere, greatly reduces dependence on non-renewablepetroleum oil, and significantly reduces non-biodegradable waste thatends up in landfills every year.

In various embodiments, the flexible foams produced hereby may beconfigured to industrially compost, rather than home compost, though itis conceivable that home composting may be of use in some instances,depending on the market. In various instances, industrial composting isuseful because it ensures that the flexible foam will last the usablelife of the resulting product it is functionalized into and notbreakdown or fall apart mid-use within the finished goods. For example,it would be detrimental for a person to purchase a pair of shoes thatwere made from the flexible foam of this invention only to have the foamdegrade during regular use before the end of the shoe's usable life.

Accordingly, in one aspect, a process of manufacturing biodegradable andindustrially compostable flexible foams, whether open-cell orclosed-cell, may be provided herein and may include one or more of thefollowing steps of: Producing a thermoplastic biopolymer blendedmasterbatch for foaming; injection molding the thermoplastic biopolymerblend into a suitable mold shape with inert nitrogen gas; using dynamicmold temperature control to ensure the optimal cell structure;controlling the biopolymer melt, pressure, and time such that adesirable flexible foam is formed; and utilizing gas counter pressure inthe injection molding process to ensure the optimal foam structure withthe least amount of cosmetic defects and little to no plastic skin onthe outside of the foamed part.

The manufacturing process of this disclosure, in concert with carefullyselected bio-derived, renewable, and recyclable feedstocks, opens thedoor to an environmentally friendly, closed-loop process. Thisclosed-loop process begins with material selection. For example, theselection of an inert and rapidly renewable polymer feedstock that isthird-party certified compostable ensures that the principals of theCircular Economy are adhered to. For these purposes, the selectedrapidly renewable polymer feedstocks begin their life as a form ofrenewable plant or mineral matter. Once converted into a suitablepolymer, these environmentally accountable precursors may be combinedwith other environmentally accountable precursors and ingredients, forfunctionalizing into a custom-made bio-polymer compound that may beemployed in the disclosed manufacturing processes.

Particularly, once the suitable bio-polymer compound is created, it isprocessed in the chemical-free manufacturing method of this disclosure.The resulting flexible foams are non-crosslinked and, in many instances,are biodegradable and compostable. Consequently, at the end of theirusable life, these produced foams may be carefully ground up into smallpieces and industrially composted in qualified facilities for breakingdown, e.g., 100%, of their composition back into useable biomass. Thisuseable biomass can then be used to grow more inert and rapidlyrenewable polymer feedstock material, and the process continues in anendless loop. Accordingly, this document describes a biodegradable andindustrially compostable microcellular flexible foam and method ofmanufacturing the same. The foam may be a closed-cell foam but can alsopotentially be formed as an open-cell foam.

In various implementations, a biodegradable and industrially compostableflexible foam can be made to have identical properties andcharacteristics of conventional petrochemical ethylene vinyl acetate(EVA) foam or the like, and yet contain a high percentage ofbiomass-carbon content. For instance, flexible EVA foam is a ubiquitousmaterial used in industry today. What makes EVA foam so prevalent is itsrelatively low cost and ease of processing while maintaining generallyacceptable technical performance properties for a given product. Thedownsides of EVA foam use are many. The material is commonly derivedfrom non-renewable feed stocks, and it is chemically crosslinked withchemical blowing agents for producing a flexible foam that is notreadily biodegradable, compostable, or recyclable.

There exist a number of configurations and embodiments that may beemployed depending on the desired physical properties, and the intendedend-use of the product, that should not be limited by this disclosure.

One factor that makes the advancements presented herein so useful isthat the biodegradable foams perform in a manner similar to EVA, and sobeing their technical performance properties are analogous to that ofEVA without the chemical additives and crosslinking. The result is acommercially acceptable flexible foam that can be a drop-in replacementfor ubiquitous EVA, but that offers a vastly reduced environmentalimpact and managed end-of-life solution that is environmentallyaccountable.

Accordingly, in one aspect a method for manufacturing a biodegradableand industrially compostable flexible foam molded product is provided.In various instances, the method may include one or more of thefollowing steps. For instance, the method may include introducing athermoplastic biopolymer blended masterbatch for foaming into a barrelof a molding apparatus. The method may additionally include introducinga fluid into the barrel under temperature and pressure conditions toproduce a super critical fluid, which upon contact with thethermoplastic biopolymer blended masterbatch produces a thermoplasticfoamed melt. Further, the method may include injecting the thermoplasticfoamed melt into a cavity of a suitable mold shape, and applying a gascounter pressure to the cavity. Finally, the cavity can be cooled toproduce the molded product.

In various instances, the introducing of one or more of thethermoplastic biopolymer masterbatch is via a sprue bushing, such aswhere the thermoplastic biopolymer blended masterbatch is produced via atwin screw extruder. In one embodiment, the thermoplastic biopolymerblended masterbatch includes one or more of polylactide acid (PLA),polyhydroxyalkanoate (PHA), cellulose acetate (CA), starch, and apetroleum-derived thermoplastic. In various instances, the fluid isintroduced into the barrel via a metering unit. In particular instances,the supercritical fluid includes one or more of nitrogen and carbondioxide. The supercritical fluid may be introduced under pressure and ata temperature, such as where the pressure ranges from about 150 bar toabout 300 bar, and the temperature ranges from about 150° C. and about350° C. Likewise, the gas counter pressure ranges from about 5 bar toabout 50 bar applied for a length of time between 1 second to 25seconds. In certain instances, the temperature may controlled viadynamic mold temperature control.

Additionally, in another aspect, an injection molding apparatus forproducing a biodegradable and industrially compostable flexible foammolded product is provided. In various instances, the injection moldingapparatus may include one or more of the following. A hopper may beincluded, such as where the hopper is configured for receiving andintroducing a plurality of thermoplastic biopolymers into the moldingapparatus, such as where the thermoplastic biopolymers form amasterbatch to be blended.

A metering unit may be included, such as where the metering unit isconfigured for receiving a fluid, and introducing the received fluidinto the molding apparatus under conditions so as to produce asupercritical fluid upon said introduction. The molding apparatus mayinclude a barrel having a first cavity configured for receiving theblended thermoplastic biopolymer masterbatch and the fluid, such thatwhen they are introduced into the barrel a thermoplastic foamed melt isproduced when the supercritical fluid contacts the blended thermoplasticbiopolymer masterbatch within the cavity of the barrel. A gas counterpressure delivery unit may also be included wherein the GCP isconfigured for delivering a gas counter pressure to the first cavity soas to control expansion of the foamed melt. Also, a mold having a cavityin fluid communication with the cavity of the barrel may also beincluded, where the cavity of the mold is configured for receiving thefoamed melt and producing the flexible foam molded product when the meltis cooled.

In various embodiments, the injection molding apparatus may include areciprocating screw that is configured to compress the foamed meltwithin the cavity of the barrel, and to convey the compressed foamedmelt into the cavity of the mold. Hence a conduit between the cavity ofthe barrel and the cavity of the mold may be present where the conduitincludes a nozzle having a sprue bushing so as to form a seal betweenthe barrel and the mold.

Accordingly, the injection molding apparatus may include one or more ofthe following: a hopper into which a thermoplastic material is suppliedto molders in the form of small pellets. The hopper on the injectionmolding machine holds these pellets. The pellets may be gravity-fed fromthe hopper through the hopper throat into the barrel and screw assembly.A barrel may also be included where the barrel of the injection moldingmachine supports the reciprocating plasticizing screw, and may be heatedby electric heater bands.

A reciprocating screw may also be present where the reciprocating screwis used to compress, melt, and convey the material. The reciprocatingscrew may include three zones: the feeding zone, the compressing (ortransition) zone, and the metering zone. A nozzle may also be present,where the nozzle connects the barrel to the sprue bushing of the moldand forms a seal between the barrel and the mold. The temperature of thenozzle may be set to the material's melt temperature or just below it.When the barrel is in its full forward processing position, the radiusof the nozzle may nest and seal in the concave radius in the spruebushing with a locating ring. During purging of the barrel, the barrelmay backs out from the sprue, so the purging compound can free fall fromthe nozzle.

Additionally, a mold and hydraulic system may also be provided. The moldsystem may include tie bars, stationary and moving platens, as well asmolding plates (bases) that house the cavity, sprue and runner systems,ejector pins, heating and cooling channels, and temperature sensor andpressure sensor. The mold is essentially a heat exchanger in which themolten thermoplastic solidifies to the desired shape and dimensionaldetails defined by the cavity. A hydraulic system may also be present onthe injection molding machine so as to provide the power to open andclose the mold, build and hold the clamping tonnage, turn thereciprocating screw, drive the reciprocating screw, and energize ejectorpins and moving mold cores. A number of hydraulic components arerequired to provide this power, which include pumps, valves, hydraulicmotors, hydraulic fittings, hydraulic tubing, and hydraulic reservoirs.

A control system may also be provided. The control system may beconfigured to provide consistency and repeatability in machineoperation. It monitors and controls the processing parameters, includingthe temperature, pressure, SCF dosing, injection speed, screw speed andposition, and hydraulic position. The process control may have a directimpact on the final part quality and the economics of the process.Process control systems can range from a simple relay on/off control toan extremely sophisticated microprocessor-based, closed-loop control.

A clamping system may also be provided. The clamping system may beconfigured to open and close the mold, supports and carry theconstituent parts of the mold, and generates sufficient force to preventthe mold from opening. Clamping force can be generated by a mechanical(toggle) lock, hydraulic lock, or a combination of the two basic types.A delivery system may also be provided. The delivery system, whichprovides passage for the molten plastic from the machine nozzle to thepart cavity, generally includes: a sprue, cold slug wells, a mainrunner, branch runners, gates, and the like.

Accordingly, in a further aspect, a system for producing a biodegradableand industrially compostable flexible foam molded product is provided.The system may include an injection molding apparatus for producing thebiodegradable and industrially compostable flexible foam molded productas described above. The system may additionally include, a supercriticalgas dosing system configured for receiving a fluid and introducing thereceived fluid into the first cavity of the barrel under conditions soas to produce a supercritical fluid upon said introduction, thesupercritical fluid producing the foamed melt when the supercriticalfluid contacts the blended thermoplastic biopolymer masterbatch withinthe first cavity. The system may further include a dynamic temperaturecontrol system configured for controlling the temperature within one ormore of the first and second cavities. A gas counter pressure deliveryunit configured for delivering a gas counter pressure to the firstcavity so as to control expansion of the foamed melt may also beincluded. Additionally, a control unit having one or moremicroprocessors may be included where the control unit is configured forcontrolling one or more of the injection molding apparatus, thesupercritical gas dosing system, the dynamic temperature control system,and the gas counter pressure delivery unit, in accordance with one ormore system parameters.

Particularly, the system components may include an injection moldingmachine system including a hopper, a barrel, a reciprocating screw, anozzle, a mold system, a hydraulic system, a control system, a clampingsystem, and a delivery system. A SCF gas dosing system may be includedand include a tank of inert gas, such as nitrogen, an air compressor, anSCF metering and control device, SCF injector, and specially designreciprocating screw, and both front and back non-return valves. Adynamic temperature control system may also be provided and include aheating unit, a cooling unit, a sequential valve, and computer-control.Additionally, there are heating elements and cooling channels locatedwithin the body of a mold, which are fed by the dynamic temperaturecontrol system, through which a heating medium or cooling mediumcirculates. Their function is the regulation of temperature on the moldsurface. And a gas counter pressure system may be provided where itincludes a tank of gas, e.g., inert gas, such as nitrogen, an aircompressor, a gas pump, a gas relief valve, a gas pressure sensor, andcomputer-control.

The system and/or any sub-systems thereof may include one or moresensors, such as including a temperature, pressure, accelerometer,gyroscope, and an orientation sensor, such as where the one or moresensors are configured for being positioned in communication with one ormore of the other components of the injection molding device, such aswithin one or more cavities of the injection molding apparatus. Invarious embodiments the sensors may be smart sensors and include acommunications module, such as with a network connection, so as toperform wireless communications. Accordingly, the system, and/or any ofits various parts may include a communications module that may becoupled to one or more of the control module, the supercritical gasdosing system, the dynamic control temperature system, and the gascounter pressure control unit, such as where the communications moduleis configured for performing one or more wireless communicationsprotocols including WIFI, Bluetooth, Low Energy Blue Tooth, and 3G, 4G,and 5G cellular communications.

In another aspect, the present disclosure describes a recyclablemicrocellular flexible foam and a method of creating the same. The foamis preferably a closed-cell foam but can also potentially be formed asan open-cell foam. Creating a recyclable microcellular flexible foamstructure begins with a suitable high-performance polymer such as thoseof polyamide origin, or the like. A non-limiting example of a suitablepolymer is polyamide 66 copolymer marketed under the trade name ofVydyne by Ascend Performance Materials, LLC, Houston, Tex. Othernon-limiting examples of suitable polymers include any number ofpolyamide block copolymers such as polyether-block-amide (PEBA), PAE,TPA, TPE-A, COPA, or the like. The aforementioned thermoplastic polymershave shown advantageous technical properties in forming themicrocellular flexible foam structure of the invention. Some of theenhanced technical properties include exceptional aging properties,excellent elongation, tensile strength, and compression set, among otherbenefits. Further, recycled feedstocks may be employed in themanufacturing of the suitable recyclable polymer or polymer blends ofthe present invention. For example, in one aspect the recyclableflexible foam thermoplastic polymer comprises at least one monomer orpolymer derived from a post-consumer or post-industrial recycledfeedstock such as caprolactam, recycled polyether block amide polymer,or the like. By way of illustration, caprolactam may be derived fromsuch recycled feedstocks by depolymerizing post-industrial orpost-consumer material containing polyamide such as fishing nets, carpetfibers, or industrial waste. Some examples of depolymerizedpost-consumer or post-industrial recycled caprolactam include ECONYL®caprolactam, whether in flake, liquid or molten, provided by Aquafil USAInc., Cartersville, Ga. The thermoplastic polymer may additionally oralternatively comprise a polyamide polymer derived from post-industrialor post-consumer polyamide carpet fiber that is collected, sorted,melted down, and reprocessed. An example of this would be to usepost-industrial polyamide carpet fiber, or the like that is collected,sorted, melted down, and reprocessed into upcycled usable polyamidematerial. An exemplary polyamide polymer derived from post-industrialcarpet fiber is Econyl manufactured by the Aquafil USA Inc.,Cartersville, Ga. Additionally, polyamide waste, may be collected fromin or around the world's oceans in the form of fishing nets, or thatlike that can then be sorted, melted down, and reprocessed into upcycledusable polyamide material. An exemplary polyamide polymer derived fromcollected post-industrial fishing nets is Akulon Repurposed manufacturedby Koninklijke DSM N.V., Heerlen, the Netherlands. It is an object ofthis invention to use recycled polymer feedstocks whenever possible.

The optimal polyamide alone cannot produce a recyclable flexible foamwithout a suitable foaming agent and foaming process. The most widelyknown foaming agent in use today is a chemical called azodicarbonamide(ADA). ADA is typically pre-impregnated into conventional thermoplasticmasterbatch resins for use in conventional injection molding foamprocesses. Unfortunately, ADA is not environmentally friendly, and it isa suspected carcinogen. Moreover, conventional foaming processes usingADA are crosslinked during the manufacturing process and thereforecreate a type of flexible foam that is not recyclable. To achieve arecyclable flexible foam, inert nitrogen gas or carbon dioxide is usedas a physical foaming agent in a modified injection molding process. Amodified physical foaming process is employed in concert with a suitablethermoplastic polymer or blended polymer masterbatch such that thepolymer or blended polymer and foaming agent work harmoniously forrecyclable and flexible foams. The preferred injection molding processof this invention utilizes homogeneous cell nucleation occurring when asingle-phase solution of polymer and supercritical fluid (SCF) passesthrough the injection gate into the mold cavity of a modified injectionmolding machine. As the solution enters the mold, the pressure dropswhich causes the SCF to come out of solution creating cell nuclei. Thecells then grow until the material fills the mold, and the expansioncapabilities of the SCF are expended. This manufacturing process runs oninjection molding machines that have been modified to allow themetering, delivery, and mixing of the SCF into the polymer to create thesingle-phase solution. Dynamic mold temperature control (DMTC) isemployed to ensure consistent cell structure within the expandingpolymer melt. DMTC can best be described as the heating elements andcooling channels located within the body of a mold, which are fed by thedynamic temperature control system, through which a heating medium orcooling medium circulates. Their function is the regulation oftemperature on the mold surface. Gas counter pressure (GCP) is alsoutilized in the process to ensure optimal foam structure with little tono skin on the resulting flexible foam. GCP can best be described as aprocess that includes a pressurized mold cavity that is injected withnitrogen gas to counteract the expansion of the gas within the melt. Asthe counter pressure is released, the gas bubbles that wouldconventionally breakthrough the surface are trapped inside, creating asmooth skin. The GCP controls the foaming through surface quality, foamstructure, and skin thickness.

The creation of the single-phase solution, in which the SCF is fullydissolved and uniformly dispersed in the molten polymer, takes placeinside the injection barrel under carefully controlled processconditions: the SCF must be accurately mass flow metered into thepolymer for a fixed amount of time. And during that dosing period, theright conditions of temperature, pressure and shear must be establishedwithin the barrel. Back-pressure, screw-speed and barrel-temperaturecontrol, as well as gas counter pressure and SCF delivery system allplay a role in establishing the process conditions that create thesingle-phase solution.

The thermoplastic polymer used to manufacture the recyclable andchemical-free flexible foams can be optionally created from any numberof polyamides or polyamide copolymers, or the like. A non-limitingexample of a suitable polymer includes polyamide 6, polyamide 6/6-6, andpolyamide 12. Alternatively, the thermoplastic polymer may comprise anynumber of polyamide block copolymers such as polyether-block-amide(PEBA), PAE, TPA, TPE-A, COPA, or the like. Any suitable polymer typemay be utilized in this invention provided that it meets the requiredhardness, moderate melt-flow, high elongation, and recyclability.

Additionally, blends of two or more thermoplastic polymers provide acombination of properties and price not found in a single polymer. Thereare a number of ways to blend polymers together successfully. One methodmay use twin-screw extrusion to melt two or more polymer resins togetherand to then extrude the molten polymer resin blend into a strand that iscooled and fed into a pelletizer for producing an array of pelletizedpieces called a masterbatch. Another method of polymer resin blending isto use compatibilizing agents to join unlike chemistries together in apolymer blend. This may use twin-screw extrusion or the like to melt thecompatibilizer and two or more polymers together in the non-limitingthermoplastic polymer types that are described above.

In one embodiment, the method includes the step of recycling theflexible foam by depolymerizing the foam into one or more monomers. Thedepolymerization process includes the steps of mechanically separatingthe thermoplastic polymer of the recyclable foam from waste, introducinga depolymerization catalyst to the separated thermoplastic polymer,heating the thermoplastic polymer and catalyst to create a distillate,separating water and resulting monomers from other byproducts, oxidizingthe aqueous monomer, concentrating the oxidized aqueous monomer,purifying the concentrated monomer, and repolymerizing the monomer tocreate a thermoplastic polymer for use in the method of making arecyclable flexible foam. The resulting monomer may include caprolactamor other monomers that may be repolymerized into thermoplastic polymers.

Depending on the application, additives may be utilized in the polymerformulations as well. For example, fillers such as precipitated calciumcarbonate, oolitic aragonite, starches, biomass, or the like may beutilized to reduce part cost while maintaining the recyclable integrityof the finished flexible foams.

Further, additional additives for use in the polymer formulations maycomprise one or more of the following. nucleating agents, such asmicro-lamellar talc or high aspect ratio oolitic aragonite, may beincluded. Such nucleating agents can greatly improve key properties ofthe resulting flexible foam by preventing cellular coalescence, loweringbulk density, and improving rebound resilience, among other beneficiallyenhanced attributes. Several non-limiting examples of nucleating agentsfor use in producing recyclable and chemical-free injection moldedmicrocellular flexible foams are micro-lamellar talc marketed asMistrocell® by Imerys Talc America Inc., Houston, Tex. and high aspectratio oolitic aragonite marketed as OceanCal® by Calcean Minerals &Materials LLC, Gadsden, Ala.

Colorants, Dyes, and Pigments may also be included. For instance,various colorants such as dyes or pigments may be used in the polymerformulations of the present invention. Several non-limiting examples arepigments that have been tailor-made for specific types of thermoplasticpolymer use, such as a wide range offered by Treffert GmBH & Co. KG,Bingen am Rhein, Germany or those offered by Holland Colours AmericasInc., Richmond, Ind.

The details of one or more embodiments are set forth in the accompanyingdescription below. Other features and advantages will be apparent fromthe description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects will now be described in detail with referenceto the following drawings.

FIG. 1 shows a foamed footwear component, namely a shoe midsoleaccording to an implementation of the present disclosure;

FIG. 2 illustrates a schematic overview of the injection moldedmicrocellular flexible foam system for producing biodegradable andindustrially compostable flexible foams, suitable for footwear;

FIG. 3 is a flowchart of a method for manufacturing biodegradable andindustrially compostable injection molded microcellular flexible foams;

FIG. 4 shows a recyclable flexible foam in accordance with the presentdisclosure injection molded to create a midsole for an athletic shoe;

FIG. 5 shows a schematic of an injection molding machine for producingthe recyclable flexible foam depicted in FIG. 4;

FIG. 6 is a flowchart of a method for manufacturing the recyclablemicrocellular flexible foam of FIG. 4; and

FIG. 7 is a flowchart showing the steps of recycling a flexible foam inconnection with an embodiment of the method for manufacturing therecyclable microcellular flexible foam of FIG. 6.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This document describes a biodegradable and industrially compostablemicrocellular flexible foam, a recyclable microcellular flexible foamand methods of manufacturing the same. The foam is preferably aclosed-cell foam but can also potentially be formed as an open-cellfoam. In various implementations, biodegradable and industriallycompostable and recyclable flexible foams can be made to have identicalproperties and characteristics of conventional petrochemical ethylenevinyl acetate (EVA) foam or the like, and yet contain a high percentageof biomass-carbon content.

Biodegradable and Industrially Compostable Injection MoldedMicrocellular Flexible Foams and a Method for Making the Same

The present disclosure relates to a process for producing abiodegradable and industrially compostable microcellular flexible foamand method of manufacturing the same. As discussed above, foamingdescribes a process that involves the trapping of pockets of gas in aliquid or solid. Generally, industry uses foaming to producelight-weight polymeric materials. This is an advantageous solution formany types of products as the foamed materials impart a multitude ofadded values such as soft cushioning, comfort, and impact protection,among others.

In various instances, it is useful for the foaming material to be in amicrocellular foam. Microcellular foam is a form of manufacturedplastic, specially fabricated to contain many, many, e.g., billions, oftiny bubbles, which may be less than about 50 microns in size. This typeof foam is formed by dissolving gas under high pressure into varioustypes of polymers to cause the uniform arrangement of the gas bubbles,regularly referred to as nucleation. The primary driver for controllingand adjusting the density of microcellular foams is the gas used tocreate them. Depending on the gas used, the density of the foam can beanywhere between about 5% to about 99% of the pre-processed bioplastic.

Accordingly, in various instances, it is useful for the foam to be aclosed-cell foam. Closed-cell foam is generally known as a cell that istotally enclosed by its walls and therefore not interconnecting withother cells. This type of material is useful as it effectively reducesliquid and gas flow from flowing through the cells. Closed cell foam,such as produced in accordance with the methods disclosed herein, isuseful for industries in which liquid resistance is critical, such ascushioning, footwear, marine, HVAC, and automotive uses.

However, in various instances, it may be useful for the foam to be anopen-cell foam. Open-cell foam is usually classified as “open cell” whenmore than half of its cells are open and interconnecting with othercells. This type of foam, which may be produced and employed in themethods disclosed herein, may be useful in that it operates more like aspring than closed-cell foam, easily returning to its original stateafter compression. The “springiness” is caused by the unrestricted airmovement and chemical makeup.

In particular instances, the foam generated and products producedtherefrom, in accordance with the described methods, functions in amanner similarly to flexible ethylene vinyl acetate (EVA) foam.Particularly, flexible EVA foam is a ubiquitous material used in themanufacturing industry today. What makes EVA foam so prevalent is itsrelatively low cost and ease of processing while maintaining generallyacceptable technical performance properties for a given product.Consequently, the foams produced in the manner herein disclosed, may beproduced at relatively low cost, with an ease of manufacturing, whilemaintaining not only acceptable, but often times superior technicalperformance products, while at the same time as being environmentallyfriendly.

More particularly, as indicated above, the downsides of EVA foam use aremany. The material is derived from non-renewable feedstocks and ischemically crosslinked with chemical blowing agents that are not readilybiodegradable, compostable, or recyclable. However, unlike flexible EVAfoams, the biodegradable and industrially compostable flexible foams ofthe present disclosure do not contain chemicals or crosslinking agents,and they are readily biodegradable and industrially compostable when theappropriate bio-derived polymers are used in their manufacture.

For instance, in various implementations, presented herein is abiodegradable and industrially compostable flexible foam that can bemade to have similar properties and characteristics of conventionalpetrochemical ethylene vinyl acetate (EVA) foam or the like, and yetcontain a high percentage of biomass-carbon content. Particularly, invarious embodiments, biodegradable, net neutral, and industriallycompostable foam precursors are used in making biodegradable andindustrially compostable flexible foams, such as in an environmentallyfriendly manner. To achieve these goals, any number of suitablebio-derived thermoplastic feedstocks may be selected for use, and may besourced from rapidly renewable feedstocks that don't typically competewith animal-feed or human food. Advantageously, as indicated, thecarefully selected bio-derived thermoplastic foam precursors have nearequivalent or equivalent technical performance properties to that ofconventionally used EVA.

A non-limiting example of such suitable thermoplastic feedstock for usein making biodegradable and industrially compostable flexible foam ofthe present disclosure with near equivalent or equivalent technicalperformance properties to that of conventional non-renewable EVA isbio-derived PBAT co-polyesters, as described herein below. Hence, invarious instances, the present devices, systems, and their methods ofuse may be employed so as to produce a biodegradable and industriallycompostable microcellular flexible foam that may be generated frombiodegradable and industrially compostable bio-derived thermoplasticresins.

More particularly, the foam precursors useful in accordance with thedisclosed methods may be any suitable type of thermoplastic resin, suchas a bio-derived thermoplastic resin or bio-derived thermoplasticcompound produced from rapidly renewably feedstocks. Such thermoplasticresins are raw, unshaped polymers that are molten and turn to liquidwhen heated, and harden and turn to solid when cooled.

The creation of thermoplastics is not a simple task. Complex chemistryand mechanical processes are required in order to make the finalproduct. In its simplest form, thermoplastics are made up of polymersand those polymers are made up of compounds. In order to produce thecompounded needed to make polymers and to then make thermoplastics,different types of molecules must be broken down and separated.Typically, foam precursors are used by feeding them into a suitableinjection molding machine in granular form. The granules are processedthrough an injection molding machine where they are liquified and shotinto a pre-formed mold cavity. Upon shot completion, the molded part iscooled and ejected from the mold in a solid-state, this process asimplemented in the present embodiments is discussed in greater detailherein below.

Bio-derived thermoplastics can be described by class. A prevalent classof bio-based thermoplastic precursors and biomass. There are two typesof bio-polyesters: polylactide acid (PLA) and polyhydroxyalkanoate(PHA). PLA is a type of thermoplastic that is made through fermentationof bacteria. PLA is actually a long chain of many lactic acid molecules.There are many different bio-derived feedstocks for producing PLA suchas sugarcane, corn, sugar beet, and lignin wood waste, just to name afew. PHA is generally produced by naturally occurring bacteria and foodwaste. There is a sub-class of PHA called polyhydroxybutyrate (PHB)which is a kind of PHA that is also widely available.

In some instances, starch or cellulose fillers, and the like can beoptionally included in the formation of bio-polyester blends as theirinclusion makes the blend more economical and, in some instances, theiruse enhances the rate of decomposition. An additional type ofbio-derived thermoplastic is known as cellulose acetate (CA). CA is asynthetic product derived from cellulose that is found in each part of aplant. Presently used feedstocks for making CA are cotton, wood, andcrop waste, just to name a few. Still further, starch is yet anothertype of thermoplastic material. Typically, starch is treated with heat,water, and plasticiers to produce a thermoplastic. To impart strength,starch is usually combined with fillers made of other materials.Presently available feedstocks for producing starch are maize, wheat,potato, and cassava. Several petroleum-derived thermoplastics are alsoknown that can be biodegradable. Common types are polybutylene succinate(PBS), polycaprolactone (PCL), and polybutyrate adipate terephthalate(PBAT), and polyvinyl alcohol (PVOH/PVA). The aforementionedpetroleum-derived thermoplastics may be produced in bio-derivedvarieties. New bio-derived feedstocks for producing PBS, PCL, PBAT, andPVOH/PVA are being produced, and are becoming commercially availablemore and more thanks to technological advancements and breakthroughs.One or more of these precursors may be generated and employed inaccordance with the methods disclosed herein.

Once the precursors have been generated, they may be foamed and used tomake one or more end products, such as via an injection molding process,as disclosed herein. For instance, in various instances, the bioderivedthermoplastic precursors may be foamed and employed in an end productproduction process, such as by injection molding. In conventional foaminjection molding, also known as direct injection expanded foam molding,thermoplastic polymers are first melted. When the thermoplastic polymersare evenly melted, a chemical blowing agent is dispersed into thepolymer melt to make the injection compound foam-able.

The homogenous polymer compound is then injected into a mold to make thefoam product. Typically, the injected polymer compound is not classifiedas a foam until an endothermic reaction in the heated mold cavityactivates the chemical blowing agent, resulting in an expanded foampart. Consequently, the mold cavity size has to be smaller than thefinal part size. The actual part expansion is created within thethermoplastic polymer formula, so that when the part is ejected from themold, it grows to the required part size.

Once the required part size is realized, it also contracts or shrinks asit cools down which often requires a secondary molding operation toobtain an accurate cooled part size. As a result, the process ofmanaging the expansion-contraction of conventional injection moldingfoams can be considered tedious, time consuming, and complex. Suchinjection molding technology can be employed to produce the precursorsand foams, as well as the products produced thereby, as discussedherein. However, in particular instances, a conventional injectionmolding machine may be modified, as disclosed herein so as to bettereffectuate the use of biodegradable, net neutral foam precursors thatmay be employed in a modified process so as to generate environmentallyfriendly foams that can be employed in producing foam products, such asfurniture cushioning, shoe components, sports equipment, and the like.

Accordingly, although the conventional process may be useful inproducing foamed products, in certain instances, it may suffer from somedrawbacks, especially with respect to the production of a compostablemicrocellular flexible foam. For instance, in various instances, atypical injection molding process, when using compostable bio-derivedthermoplastic resins to produce a compostable flexible foam may bedeficient in various different manners. For example, the above mentionedconventional non-modified foam injection molding process may bedeficient and unsuitable for producing biodegradable and compostableflexible foams. A primary reason for this stems from the very nature ofthe conventional non-modified foam injection molding in which thepolymer compounds are crosslinked during their manufacture.

As indicated above, crosslinking can be described as the formation ofcovalent bonds that hold portions of several polymer chains together,occurring at random. The result is a random three-dimensional network ofinterconnected chains within the foam matrix. This crosslinked foamcannot readily be un-crosslinked, and thus, the various precursoringredients cannot easily be separated back to their individual typesand biodegraded or composted. As a result, the presently disclosedadvantages would not readily be achievable without changing the foamingapparatus and its methods of use in manufacturing. Accordingly, amanufacturing machine and process of using the same to generate foams ina manner that is suitable for employing non-crosslinking precursors inan injection molding process is presented herein.

Consequently, in one aspect, presented herein is a new injection moldingmachine. The molding machine may be configured so as to employ a varietyof flexible foam compositions, including bioderived thermoplasticprecursors, that can be foamed in such a manner as to produce acompostable microcellular flexible foam structure, via application ofthe precursors into the new injection molding machine, which can then beused to produce one or more flexible foamed products. Hence, in oneaspect, provided herein is a new injection molding machine.

Some of the factors that sets the manufacturing machinery of the presentdisclosure apart is the use of specialized auxiliary equipment coupledwith a microcellular gas dosing system that may be affixed to andthereby modify and improve a standard injection molding machine.Essentially, as presented herein a standard injection molding machinehas been overhauled and retooled to function in a suitable manner foruse in accordance with the present disclosure. The general method formodification begins with transforming the injection molding screw on theinjection molding machine to be able to handle supercritical inert gas,such as nitrogen, CO2, and/or non-reactive and/or inert gasses.

A gas dosing system may then be equipped to the injection moldingmachine for dosing the proper gas at the appropriate amount into thepolymer melt within the screw, such as prior to injection into thetemperature controlled mold cavity. Additionally, a specialized moldcavity may be utilized in which the thermal temperature cycling of themold can better control the resulting foams outer skin texture and skinthickness, as well as reducing the cycle time for part production.Further, an auxiliary gas counter pressure system may be equipped to theinjection mold machine for forcing an inert gas back into the mold tocounteract the liquid polymer melt being shot into the mold.

This counter pressure is useful for ensuring that the molten injectionshot substantially, if not completely, fills the mold cavity andprevents part warping and shrinkage, as well as controlling celldistribution and cell density. Further, the appropriate counter pressurehas a beneficial influence on skin texture and skin thickness of thepart. Consequently, when the part is ejected from the mold cavity thereis no discernable shrinkage and no secondary steps required forimmediately using the molded foam part. Beneficially, the part is notcrosslinked and as a result, it can biodegrade or compost provided thatthe suitable bio-derived polymer compounds are used in the foamscreation.

In view of the above, in one aspect, the present disclosure is directedto creating a biodegradable and compostable, e.g., industrially,microcellular flexible foam structure. Particularly, in one embodiment,the process begins with a suitable biopolymer or biopolymer blend. Forinstance, in various instances, a biopolymer may be one or morepolymers, such as produced from natural sources, either chemicallysynthesized from a biological material or entirely biosynthesized byliving organisms.

There are primarily two types of biopolymer, one that is obtained fromliving organisms and another that is produced from renewable resourcesbut require polymerization. Those created by living organisms includeproteins and carbohydrates. Unlike synthetic polymers, biopolymers havea well-marked structure. This type of polymer is differentiated based ontheir chemical structure. What makes the biopolymers of the presentdisclosure particularly useful is that they closely mimic non-renewableEVA in terms of technical performance properties.

Likewise, in particular instances, a biopolymer blend may be employed ingenerating the foam structure, such as where the biopolymer blend may bea custom compound of two or more biopolymers. Several non-limiting typesof biopolymers are sugar-based biopolymers, starch-based biopolymers,biopolymers based on synthetic materials, and cellulose-basedbiopolymers. The typical ratio of the biopolymer blended combinationswould depend on the type of product being manufactured and the requiredtechnical properties of the resulting part.

More particularly, in a particular embodiment, a biopolymer blend thatcan be used as a foam precursor includes a plurality of resins, such asone or more solid or viscous materials that can be added to the melt toa polymer, such as after curing. Hence, after polymerization or curing,resins form polymers. For instance, a suitable resin may be one or moreof: Aliphatic and Aliphatic-aromatic co-polyester origin. Generallyspeaking, aliphatics or aliphatic compounds relate to or denote organiccompounds in which carbon atoms form open chains instead of aromaticrings. Likewise, suitable aliphatic-aromatic compounds are generally arandom combination of open chains of carbon atoms (the aliphaticportion) and a stable ring or rings of atoms (the aromatic portion).

Typically, the amount of aromatic acid in the chain is lower than 49%,though recent technological advances have shown great promise forincreasing this and further aiding in the biodegradation. An example ofan aliphatic-aromatic is aliphatic-aromatic copolyester (AAPE) that canbe produced from any number of non-renewable and renewable feedstocks,although, renewably-sourced AAPE is particularly useful. Accordingly, invarious embodiments, one or more of these aliphatics and/or aliphaticsmay be of co-polyester origin. Such co-polyesters are created when apolyester is modified. For instance, co-polyesters are produced whenmore than one diacid or diol is used in the polymerization process. Inthe case of aliphatic-aromatic co-polyesters, a combination of precursorchanges are made to essentially hybridize or “bridge” thealiphatic-aromatic chain and combining more than one additionalprecursor in the polymerization process.

A non-limiting example of a suitable biopolymer blend is polylactic acid(PLA) and poly(butylene adipate-co-terephthalate) (PBAT). Polylacticacid (PLA) is a biodegradable thermoplastic aliphatic polyester derivedfrom renewable biomass. Typical feedstocks used in the creation of PLAinclude fermented plant starch such as corn, cassava, sugarcane, sugarbeet pulp, and to a lesser degree lignin wood waste. Likewise,Polybutylene adipate terephthalate (PBAT) is a biodegradable randomcopolymer, specifically a co-polyester that is commonly derived fromadipic acid, 1,4-butanediol and terephthalic acid. It is advantageous touse renewably-sourced PBAT rather than PBAT sourced from non-renewablepetroleum sources. In various instances, one or more of these componentsmay be blended.

Blends of two or more thermoplastic biopolymers provide a combination ofproperties and price not found in a single polymer or co-polymer. Thereare a number of ways to blend biopolymers together successfully. Acommon method is to use twin-screw extrusion to melt two or morebiopolymer resins together and to then extrude the molten biopolymerresin blend into a strand that is cooled and fed into a pelletizer forproducing an array of pelletized pieces called a masterbatch. Anothermethod of biopolymer resin blending is to use compatibilizing agents tojoin unlike chemistries together in a biopolymer blend. Commonly, thistoo uses twin-screw extrusion or the like to melt the compatibilizer andtwo or more biopolymers together in the process described above.

Accordingly, it has been determined herein that the aforementionedblended thermoplastic biopolymer resins show advantageous technicalproperties in forming an optimal microcellular flexible foam structureof the disclosure. Some of the enhanced technical properties include:acceptable aging properties, excellent elongation, and exceptionalcompression set, among other benefits. For instance, an advantage of theuse of biopolymer blends, as disclosed herein, is the enhanced technicalperformance properties that result from the formation and use of a givenbiopolymer blend. Specifically, enhanced properties such as improvedelongation, tensile strength, impact strength, and melt-flow, just toname a few, can all be realized when the right combination ofbiopolymers, and/or biopolymer-compatibilizer blends are realized.

Accordingly, these resins may be employed in accordance with the methodsand machines disclosed herein so as to produce a foaming agent. Hence,in one aspect the present disclosure is directed to a foaming process.As described above, the machines and processes disclosed herein may beconfigured for performing a foaming operation whereby pockets of gas aretrapped in a liquid or solid, which foaming may be used to producelightweight polymeric materials. This is an advantageous solution formany types of products as the foamed materials impart a multitude ofadded values such as soft cushioning, comfort, technical athletic gear,including shoe components, and impact protection among others. However,in various instance, the aforementioned optimal aliphatic andaliphatic-aromatic co-polyester biopolymers or biopolymer blends aloneare useful for producing a flexible foam, in various instances, theiruse in the production of a flexible foam may be enhanced by theinclusion of a suitable foaming agent within the foaming process.

For instance, a widely known foaming agent in use today is a chemicalcalled azodicarbonamide (ADA). Azodicarbonamide is typicallypre-impregnated into petrochemical thermoplastic masterbatch resins foruse in conventional injection molding foam processes. Particularly, thepre-impregnation of a chemical blowing agent such as ADA are typicallyincluded in the bioplastic blend prior to foaming. The reason for thisis that the pre-impregnation of a chemical blowing agent, such as ADA,is needed as conventional injection mold foaming does not allow for thecustomization of the foam molding variability. That is, chemical blowingagents such as ADA are limited in their ability to modify or influencethe physical aspects of the foaming process during the point ofmanufacture.

Inversely, the specialized foaming process of this disclosure benefitsfrom the physical foaming that a noble or inert gas, such as nitrogen,provides. In this process, the gas, e.g., nitrogen, dosing can beadjusted in concentration within the biopolymer melt and this has adirect influence on the foaming outcome, which can be seen as a majoradvantage to customize specific aspects of the resulting foam. Althoughthere exists several petrochemical-derived thermoplastics which areknown to be biodegradable and industrially compostable, such as PBATco-polyesters, it is advantageous to use renewably-sourced feedstockssuch as the line of neat PBAT co-polyesters.

For instance, in producing a foaming agent, it may be useful to firstproduce a custom-made masterbatch, such as a bioplastic blend that istailored to produce a given type of biodegradable and industriallycompostable flexible foam for a given product type. For example,different types of custom-made masterbatch compounds may be produced fordifferent types of product applications. This can be explained byindicating that what works for making a particular type of foam in apair of shoes, for example, may be different from what is needed formaking a particular type of foam, such as for use in making a piece offurniture. Further, custom-made masterbatches can each contain differentcolorants for a given product use. Here again, different product typesneed different aspects of customization, and the ability to produceuniquely separate masterbatches is highly advantageous for theseparticular uses.

Unfortunately, ADA is not environmentally friendly, and it is asuspected carcinogen to human health. Consequently, its use in thepresent methods and the products produced thereby is limited in itsadvantages. Moreover, conventional petrochemical thermoplasticmasterbatch resins are not biodegradable nor industrially compostable,and thus, their advantages are also limited. In view of thesedeficiencies in the use of ADA and conventional petrochemicals forproducing masterbatch, presented herein are biodegradable, industriallycompostable, thermoplastic biopolymer resins that may be used to producemasterbatch for generating a biodegradable and industrially compostablemicrocellular flexible foam.

In various instances, as discussed above, to achieve a more optimalbiodegradable and industrially compostable flexible foam for the use inmanufacturing molded end products, e.g., in an environmentally emissionneutral manner, a supercritical fluid can be injected by the system intothe molding process. Specifically, a supercritical fluid is a substance(liquid or gas) that is in a state above its critical temperature (Tc)and critical pressure (Pc). At this critical point gases and liquidscoexist, and a supercritical fluid shows unique properties that aredifferent from those of either liquids or gases, e.g., under standardconditions. It is advantageous to use inert supercritical fluid, such asnitrogen, CO₂, He, Ne, Ar, Xe, and other such inert gasses, such as in asupercritical fluid state, which gasses that may be employed inaccordance with the methods disclosed herein as a blowing agent in thefoaming process.

The aforementioned supercritical fluid works by solubilizing in thepolymer matrix within the injection molding machine barrel. As thespecialized injection molding process injects the liquid bioplasticcompound into the injection mold cavity under controlled pressure andtemperature, the gas forces the polymer melt to fully expand to themaximum limits of the mold cavity. In this process, the gas is usefulfor maximizing the cell structure of the polymer matrix within thefoaming process. This maximization of the specialized foaming processensures that undesirable sink marks or warping within the final foamedpart is minimized. This is very different than conventional chemicalblowing agent-produced flexible foams in that conventional blowingagents are not subjected to the same type of supercritical states orpressures, and therefore the conventionally-produced foams lackconsistency in the final foamed part, and they may contain undesirablesink marks and warping.

More particularly, in various instances, an inert gas, such as nitrogenor carbon dioxide, can be formulated in a supercritical fluid state,which may then be used as a physical foaming agent, such as in the novelinjection molding machines and processes discussed herein. In such aninstance, the disclosed modified physical foaming process may beemployed in concert with: a suitable thermoplastic biopolymer or may beblended biopolymer master batch, such that the biopolymer or biopolymerblend and foaming agent work harmoniously for producing the most optimalbiodegradable and industrially compostable flexible foams.

The suitable biopolymers, bioplastics, and bioplastic-blends of thepresent disclosure may be derived from renewable resources, such asthose that do not compete with animal-feed and human food, and thosethat are derived from waste streams of renewable resources. Anon-limiting example of a suitable biopolymers finding use in producingthe biopolymer or biopolymer blend consist of polylactic acid (PLA),poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate)(PBAT), polycaprolactone (PCL), polyhydroxy alkanoate (PHA),polybutylene succinate (PBS), polycaprolactone (PCL), polybutylenesuccinate adipate (PBSA), polybutylene adipate (PBA), and thermoplasticstarch (TPS). Suitable biopolymer blends of the present disclosure areany combination of the above listed biopolymers and bioplastic types, aswell as any hybrid biopolymer blends consists of biomass-containingpoly(butylene adipate-co-terephthalate) (PBAT). A non-limiting exampleof this would be a lignin-containing PBAT blend where the lignin issourced from wood waste and the PBAT is sourced from renewableresources.

Accordingly, in various embodiments, the injection molding devices andmethods of their use disclosed herein are useful for producing foamshaving homogeneous cell nucleation. As discussed, the apparatuses andtheir methods of use disclosed herein may be used to produce homogenouscell nucleation so as to produce a foam whereby the foam nuclei arerandomly and spontaneously generated, and thus grow irreversibly in asingle phase solution system that has minimal to no impurity. Forinstance, as set forth herein below, in one aspect a process ofmanufacturing flexible and/or rigid foams is provided. The method may beimplemented so as to derive an open-cell or closed-cell foam, such aswhere the foam has inherent compostable, antimicrobial and/or flameresistant properties.

In certain instances, the method may include one or more of the steps offorming master batch, such as including blending one or resins, e.g.,copolymer carrier resins, and various foaming ingredients. In asubsequent step, the method may include adding a antimicrobial compoundsuch that the foam material may be used in the production ofantimicrobial, antibacterial, and/or antiviral footwear components,furniture components, yoga mats, apparel, sporting good components,medical devices, and/or flame resistant articles of manufacture, andother suitable uses. Particularly, in accordance with the methods hereindisclosed, the produced products may be used in a vast array ofapplications, and generally their production method can be broken downinto three distinct phases. First, the bulk polymer product is made.Next, the polymer is exposed to various processing steps. Finally, thepolymer is transformed into its final product, such as clothing,anti-microbial carpets, furniture, car components, yoga mats, shoecomponents, including, soles, midosles, insoles, and the like.

Particularly, this single phase solution may be employed so as toproduce nucleation sites where the cells grow and are expanded by thediffusion of gas into bubbles. The machines and processes disclosedherein are particularly useful to initiate a foaming process thatresults in the generation of homogenous cell nucleation in a manner suchthat small bubbles are uniformly dispersed within the foam matrix.Specifically, unlike conventional foaming, the supercritical fluidformed flexible foams of the present disclosure benefit from greatlyimproved mechanical properties that may be directly attributable to thesmall bubble sizes. More specifically, the devices and methods disclosedherein are configured to produce bubble diameters are on the order of100 microns or more to about 1 micron or less, such as about 50 micronsto about 10 microns, or less, such as from about 20 to about 40 microns,including about 30 microns and they are produced by the use ofthermodynamic instabilities, and all without the use of a conventionalchemical blowing agent in the foam's creation.

For instance, in a particular embodiment, the system may be configuredfor using the present novel injection molding machine disclosed hereinfor producing a biodegradable and industrially compostable microcellularflexible foam having a homogeneous cell nucleation that may occur when asingle-phase solution of biopolymer or biopolymer blend andsupercritical fluid (SCF) passes through the injection gate into themold cavity of the injection molding machine. Specifically, as explainedin greater detail herein below, the present injection molding machinesare configured for producing a molten material, such as by injecting amold precursor into a mold for producing a finished part or componentpart. The injection molding machine may include a material hopper, aninjection ram or screw-type plunger, and a heating unit. Such injectionmolding machines are rated in terms of tonnage, which expresses theamount of clamping force that the machine can exert.

Accordingly, the process may begin with a granular bioplastic compoundbeing fed by a forced ram from a hopper into a heated barrel. As thegranules are slowly moved forward by a specialized reciprocatingscrew-type plunger, a supercritical fluid is introduced through aninjector by way of a separate supercritical metering auxiliary machinethat may be connected directly to the injection molding apparatus thatfeeds into the screw. Consequently, the supercritical fluid saturateswithin the biopolymer melt during screw rotation and this creates asingle-phase solution.

The molten mixture is then forced into a heated chamber with high backpressure where it is melted at a temperature that is controlled by acomputer interface. As the plunger advances, the melted bioplasticcompound is forced through a nozzle that rests against the mold,allowing it to enter the mold cavity through a gate. Hence, the presentfoaming process may be configured for subjecting polymeric materials toa mechanical or physical process by which heat and pressure are appliedto the polymeric materials in the presence of a blowing agent. Theblowing agent can be of chemical origin, as is the case withconventional closed-cell EVA foaming, or it can be of inert origin, asis the case with the biodegradable and industrially compostable flexiblefoams of the present disclosure. Accordingly, in view of the forgoing,as the solution enters the mold, the pressure drops, which causes theSCF to come out of solution creating cell nuclei.

Particularly, the supercritical fluid saturates within the biopolymermelt during screw rotation and this creates a single-phase solutionunder certain temperature and pressure. The molten mixture is forcedinto a heated mold chamber with high back pressure and the pressure ofthe single-phase solution is dropped from microcellular process pressureto atmospheric pressure, thus rapid pressure unloading occurs. Thenucleation phenomena occur due to the gas separating out of the mixture.At this point, the nuclei grow into stable bubbles. The bubble size isdetermined by the saturation, microcellular process pressure, and themixing temperature, which may all be controlled by the present systemand methods. Consequently, when millions of nuclei are generated and thenucleus is stable, the bubble growth starts.

The bubble morphology is determined by the SCF concentration as well asthe injection molding process parameters. Hence, these parameters may beselected for control by the system so as to produce a useful and/ordetermined bubble morphology. As the molding of the part concludes, themold is cooled and the melt temperature decreases, which forces the meltto freeze up and solidify. Again, these parameters may be tightlycontrolled by the system, such as depending on the end products to beproduced. Specifically, at this point the bubbles stop growing and theshape of the resulting part is fixed. The cells then grow until thematerial fills the mold, and the expansion capabilities of the SCF areexpended.

Accordingly, in this process, the molten biopolymer and SCF blend arecontrollably shot into the heated mold cavity and a sudden pressure dropis experienced. Millions of tiny bubbles are produced out of the nucleigrowth and these bubbles physically force the molten mixture to expandto the maximum constraints of the mold cavity. As the molten mixtureexpands to the maximum physical potential, the material is rapidlycooled within the mold and the bubbles stop forming, the molten mixturestops expanding, and a final solidified part is formed. All of thistakes place in a matter of seconds within the injection molding system.

As indicated, this manufacturing process runs on the above describedinjection molding machines, which have been modified to finely control:metering, delivery, mixing, temperature, pressure, injection, speed, andthe like. For instance, an auxiliary metering unit may be used tocontrol metering for delivering accurate SCF gas dosing into the polymermelt. Specifically, a suitable gas dosing auxiliary machine may beconfigured to convert the inert gas into a supercritical fluid state,and to meter the dosing of the SCF delivery into the injection moldingmachine, such as by way of computer control mechanism.

For example, an operator or suitably configured microcontroller canprogram the gas dosing auxiliary machine to a pre-determined SCF gasdosing amount. Essentially, a gas dosing auxiliary machine is a SCFdelivery system that may be electronically and/or physically coupled tothe injection molding machine. Particular, a suitable SCF gas dosingauxiliary machine for use in the present disclosure may be configured toproduce a line of gas dosing systems that are designed to convertindustrial grade Nitrogen or other inert gasses into a supercriticalfluid. The gas dosing apparatus may be configured to precisely dose andinject the SCF into the injection molding machine at a pressure of up toand even over 275 bar.

To operate the gas dosing apparatus, an operator may employ anassociated computing device, such as a desktop or laptop computingdevice, that is configured for producing a graphical user interface(GUI) for controlling the system apparatuses and respective controlparameters, such as the dosing apparatus. For instance, an operator mayenter the selected parameters, e.g., the desired SCF gas dosing shotparameters into the GUI. A processing element of the system thencalculates all subsidiary parameters in real-time and optimizes the SCFdelivery into the injection molding machine. Consequently, the controlunit of the system ensures that the gas dosing system and injectionmolding machine work symbiotically together, such as through a networkof computer-controls. Hence, this gas dosing system is a uniqueattribute of the present disclosure as the supercritical inert gas canbe effortlessly used as a physical blowing agent for producing thebiodegradable and industrially compostable flexible foams of the presentdisclosure in substitution of chemically-reactive blowing agents used inconventional flexible foams. This control of the mixing of the SCF intothe biopolymer is useful for creating the single-phase solution.

Further, during the injection molding process of the present disclosure,SCF is injected into the polymer melt. A single phase of polymer-SCFmixed solution is obtained under definite temperature and pressurewithin the injection molding machine screw and barrel. The temperatureand pressure may be variably controllable and relate directly to thetype of flexible foam being produced and for what type of applicationthe end product will be used. In this stage, the concentration of SCF isdetermined by saturation, microcellular process pressure, and the mixingtemperature. An example can be provided for making a biodegradable andindustrially compostable flexible foam of the present disclosure for usein making a foamed furniture, automotive, athletic, and/or shoe part,specifically a shoe midsole. A non-limiting example of a suitablebiopolymer blend for use in this non-limiting example is rapidlyrenewable PBAT bio-polyester formed into a biopolymer compound.

Accordingly, the granulated biopolymer compound is first fed into theinjection molding machine via the hopper. Next, the biopolymer is slowlymoved through the injection molding machine screw and barrel when aspecific SCF gas dosing is introduced and homogenously mixed into thenow molten biopolymer compound, completely saturating it. The moltenbiopolymer compound and SCF are now a single-phase solution. Anon-limiting example of the initial SCF gas concentration may beCo=0.25% with a melt temperature range of between 176° C. and 250° C.,and more preferably in the range of 180° C.

Additionally, in various embodiments, the temperature within the moldcan be finely controlled along with the pressure, such as in a dynamicmold temperature control (DMTC) protocol. For instance, a DMTC processmay be employed to ensure consistent cell structure within the expandingbiopolymer melt. Particularly, DMTC may be configured so as to includethe rapid changing and controlling of the mold temperature and/orpressure during the injection filling stage. This thereby dynamicallycontrols the mold temperature and/or pressure in terms of both hot andcold thermal cycling, with or without pressure.

For instance, the control module of the system may be configured so asto control the mold temperature during the injection filling stage, forinstance, in such instances, a dynamic mold temperature control may beemployed. More particularly, compared with conventionally knowninjection molding processes, an important characteristic of the dynamicmold temperature control employed herein is that the mold temperatureitself may be dynamically controlled. Before melt injection of thesingle-phase solution, the mold may first be heated to a preset upperlimit. During the melt filling stage, the temperature of the mold cavitysurface may be kept higher than the upper limit to prevent the melt fromsolidifying prematurely. When the melt filling process has concluded,the mold is cooled quickly to a lower limit (the ejection temperature),and then the molded foam part is ejected out the mold cavity.

Dynamic mold temperature control (DMTC) as implemented herein reliesupon a control method based on rapid electrical rod heating and rapidwater cooling. Specifically, the DMTC employed by this disclosureconsists of five main components: an air compressor, a valve-exchangedevice, a computer-controlled mold temperature control unit, anelectrically heated mold, and a cooling tower. The cooling tower may beused to supply sufficient water cooling to the mold. The air compressoris used to produce compressed air as the driving gas of pneumatic valvesand to exclude residual cooling water from entering the mold aftercooling. The valve exchange device is used to switch the valves totransfer different mediums from pipelines to the mold, such as hot andcold thermal cycling.

Accordingly, in various instances, the machines and processes herein mayinclude pipes and other conduits for the passing of reacting materials,which conduits are associated with one or more heat exchange units, soas to heat and/or cool the reactants as they are pumped into and/orthrough the conduits and pipes. In such an instance, the exchanger maybe controlled to adjust the temperature to the reactive level. On oneend of the pipe a dispensing head may be included, which may beassociated with one or more valves. Further, the dispensing head may behooked up to a processing line. The electrically heated mold is used formolding the final shape of the foamed parts. The function of the moldtemperature control is to control the heating and cooling of the mold;all of this is coordinated with the injection molding machine bycomputer-control.

Likewise, as indicated, the pressure can also be finely controlled, suchas via a gas counter pressure (GCP) protocol. For instance, a GCPprotocol may be utilized in the manufacturing process so as to betterensure the optimal foam structure of the end product, and to do so in amanner that there is little to no skin on the resulting flexible foam.For instance, using this GCP process a pressurized mold cavity may beinjected with an SCF, which alone and together may function tocounteract the expansion of the gas within the melt. Particularly, asthe counter pressure is released, the gas bubbles that wouldconventionally breakthrough the surface are trapped inside, creating asmooth skin.

This gas counter pressure process prevents the gas bubbles fromcontacting and breaking through the surface of the foaming material asthe foamed part is formed. This is achieved by the counteractingpressure being applied by the GCP system into the mold cavity at oraround the same time of the molten single-phase solution injection shotand hold time. The inert gas bubbles are subjected immense forces andtherefore the molten single-phase solution isn't given the opportunityto release the trapped bubbles to the outside of the foamed structurewhile being formed. The result is molded foam part with cosmeticallysmooth skin formed on the outside of the part.

Accordingly, as implemented herein, the controller of the system mayimplement a gas-counter pressure (GCP) procedure that is configured toimprove the control of the foaming process by applying different gaspressures at the melt-injection stage of foam injection molding. Forinstance, by controlling the various components of the system, thecontrol system may be configured to apply varying screw-contained SCFsingle-phase solution pressures and GCP pressures, such as in concertwith proper shot sizes, shot hold times, melt temperatures, and moldtemperatures.

In this manner, an entire system is created by which high-quality andcommercially acceptable biodegradable and industrially compostableflexible foam parts may be produced. Specifically, subtle changes to theGCP pressures affect the surface quality of the foam. For example,without the use of GCP, the formed bubbles in the polymer melt locatedwithin the mold cavity could release and the cosmetic appearance of theresulting foamed part might not be acceptable. Additionally, without theuse of GCP the skin thickness could be undesirably thick as there wouldbe no counter pressure to counteract the rapid cooling of the moltensingle-phase solution as it is expanded into the mold. Particularly, thesingle-phase solution would hit the steel mold boundaries during theinjection shot and instantly solidify with an undesirable thick skinthat would not be acceptable for most commercial applications. In sum,process parameters have a demonstrable impact on the final partsquality. Accordingly, in these manners, this GCP process can beimplemented in a manner to control the foaming, such as through one ormore of surface quality, foam structure, skin thickness, and the like.

Hence, in various embodiments, the system may be configured so as toproduce a SCF in a manner so as to form a Single-Phase Solution.Particularly, in various embodiments, a single-phase solution iscreated, in which the SCF may be: fully dissolved and uniformlydispersed in the molten biopolymer, which takes place inside theinjection barrel under carefully controlled process conditions. Forinstance, as discussed the formation of a single-phase solution iscritical for producing consistent mass-producible molded foam parts ofthe present disclosure.

Consequently, the injection molding system process should be configuredto be controllable and repeatable in a very consistent manner. Toachieve this, the first line of defense is to ensure that the biopolymercompounds and the SCF are homogenously mixed into a single-phasesolution, such as where the single-phase solution is fully saturated anddispersed within the biopolymer melt within the injection moldingmachine barrel. Once a single-phase solution is achieved, the system canreliably input the desired shot weight, shot hold time, and GCP gasdosing for customizing an endlessly reproducible molded foam part in atime-optimized and mass-producible manner.

So being, the SCF should be accurately mass flow metered into thebiopolymer for a fixed amount of time. For instance, the system controlmodule may be configured such that during the dosing period, the rightconditions of: temperature, pressure and shear are established withinthe barrel. Likewise, the back-pressure, screw-speed andbarrel-temperature can be finely controlled by one or more controlelements of the system. Additionally, the SCF delivery system can bemodulated so as to establish the process conditions that create anoptimal single-phase solution.

For instance, as discussed above, the control module may be communicablycoupled to a system associated mass flow metering device that isconfigured to measure mass flow rate of a fluid traveling through one ormore vessels, e.g., tubes, of the system. The mass flow rate is the massof the fluid traveling past a fixed point per unit time. As it pertainsto the present disclosure, the principals of mass flow metering areimplemented to ensure consistent repeatability in the foam moldingprocess. Specifically, as described above, a specially designed injectoris coupled to the injection molding barrel that is capable of beingcontrolled by computer-controlled programming of a processor of thesystem. Consequently, the system can be configured to implement aspecific SCF gas dosing delivery into the biopolymer melt and thecomputer-controlled program can optimize the delivery based on thecollection of real-time data from the mass flow rate, such as throughfeedback from one or more system sensors. This use of mass flow meteringensures the most optimal process controls for the single-phase solutionof the present invention.

Accordingly, during the dosing period, the temperature throughout thesystem, such as within the barrel, may be controlled so as to be between100° C. and 600° C., such as between 200° C. and 500° C., for instance,between 300° C. and 400° C., and more particularly, between the rangesof 320° C. and 380° C., including between 360° C. and 380° C. within thebarrel. Likewise, the SCF delivery pressure may be finely controlled soas to be in a range of between 1,000 and 8,000 PSI, such as between1,500 and 6,000 PSI, for instance, between 2,000 and 5,500 PSI,particularly, between 3,000 and 4,000 PSI, and more particularly betweenthe ranges of 2,600 and 2,800 PSI.

In this manner, the control module may be configured such thattemperature and pressure work in concert to generate the optimal nucleiand the resulting bubbles within the biopolymer melt and resultingfoaming matrix. Additionally, with respect to shear, shear isestablished within the barrel when layers of molten biopolymer flowrelative to each other. Hence, during injection, the molten biopolymercompound may be flowed through the melt delivery channel of the barrelnozzle, such as before entering the mold like a fountain.

Shearing is the stretching of the biopolymer between the rotating screwand the stationary barrel, causing heat to develop within the material.Hence, shear should be controlled in the injection molding process.Consequently, one or more controlling units of the system may beconfigured such as for controlling the injection velocity, the filltime, and the tolerance therein so as to achieve the right conditionsfor producing a given biopolymer compound, with a given injectionmolding machine size, and with a given injection molding machine screwand barrel size.

The back-pressure may also be controlled. For instance, back-pressure isthe pressure in an injection molding machine that is exerted by thebiopolymer when it is injected into the mold. Specifically,back-pressure is resistance applied to the injection screw as itrecovers to load the next biopolymer shot into the mold. As indicatedabove, the various parameters of the system may be configured so as tocontrol and/or modulate the back pressure.

Further, a controller of the system may be configured to control andmodulate the screw-speed. The screw speed may be controlled bycomputer-control. As indicated, during the initial phase of injectionmolding operation, the screw rotates within the barrel to homogenize themelting biopolymer compound mixture in concert with the SCF gas. Anon-limiting example of the screw speeds of the present disclosure maybe from 1 or 5 or 10 to 75 or 100 or 200 rpm, for instance, from 20, 25,or 30 to 40, 50 or 60 rpm.

The system may include a heating and/or cooling control unit that may beassociated with the barrel, so as to control the temperature therein.Accordingly, the control module may be configured to controlbarrel-temperature. Hence the barrel temperature may be controlled so asto make the temperature therein hotter or colder as necessary for thefoaming process.

Accordingly, in view of the above, the SCF delivery system may include acontrol unit that is configured to control a combination of SCF deliverypressure and the SCF dose weight, which is typically measured in grams.The SCF pressure and dose may be controlled in a manner so as to affectthe single-phase solution. That is, the smaller the SCF dose, the lessSCF saturation need be within the biopolymer melt, whereas the largerthe SCF does, the more SCF saturation need be within the melt. Likewise,the lower the SCF delivery pressure, the lower the uptake of thesaturation, and therefore the lower the growth of the nuclei that cangrow to form bubbles within the molten biopolymer melt. And the greaterthe SCF delivery pressure, the greater the uptake of the saturation, andtherefore, the greater the growth of the nuclei that can grow to formbubbles within the molten melt.

With respect to saturation, the system and apparatus is configured fordelivering a gas to the melt chamber under a temperature and a pressuresuch that a supercritical fluid is formed and saturates within thebiopolymer melt, such as during screw rotation. Consequently, asingle-phase solution is created under a controlled temperature andpressure. Specifically, a single phase of polymer-SCF mixed solution maybe obtained herein under definite temperature and pressure within theinjection molding machine screw and barrel. More specifically, thesystem controller may variably control the temperature and pressure in amanner that is dependent upon the type of flexible foam being producedand for what type of end-product is being produced.

In this stage, the concentration of SCF may be determined andcontrolled, such as by a feedback loop, whereby the amount of saturationis determined, such as via a sensor, which evaluates saturation processprogression and then modulates microcellular process pressure and themixing temperature based on achieving a determined set point forsaturation level. In such an instance, the supercritical fluid (SCF)controllably saturates within the biopolymer melt during screw rotationand this creates a single-phase solution under definite temperature andpressure. SCF is one part of a two-part molten biopolymer compoundmixture and it is used as a physical blowing agent in the presence ofdefinite pressure and temperature in the present injection mold.

Accordingly, in view of the above, in one aspect, provided herein is amachine and method of using the same for the production of abiodegradable and industrially compostable microcellular flexible foam.Particularly, in one instance, the foam is produced and/or used in theproduction of foamed products, such as via a microcellular injectionmolding (MuCell) process, e.g., MuCell manufacturing. MuCellmanufacturing employs a supercritical fluid, as described above, that issubjected to extreme pressure and dissolved into a polymer melt within ascrew barrel of a manufacturing tool, such as described below, which isconfigured for optimizing SCF dosing for the purpose of generating amolten biopolymer melt that us heated to a liquid state.

Hence, at the heart of the injection molding machine is the injectionmolding machine barrel and the screw contained therein, both commonlymade from tool steel. The barrel is the main delivery portal for thepresent single-phase solution prior to being metered and then pressed or“shot” into the dynamically temperature controlled mold component.Consequently, the biopolymer melt is delivered into the barrel throughthe injection molding machine hopper. And the system controller feeds agiven amount of granular bioplastic pellets into the hopper as one ofthe first steps in the injection mold machine operation.

Specifically, during injection, the SCF vaporizes and becomes gasbubbles, e.g., foam in the form of a finished molded parts. Because thebubbles reach micron sizes, the process produces microcellular foaming.The process described herein is advantageous over conventional injectiontechnologies, because it results in a resultant product that evidencesone of more of the following: less shrinkage, light weight products,with few sink marks, and can be generated by low cost precursors. Morespecifically, with regard to less shrinkage, shrinkage can be controlledby understanding that volumetric shrinkage is caused by thermalcontraction, which affects all polymers, and thus, shrinkage can beavoided by tracking shrinkage progress, via a system sensor, and finelycontrolling the barrel conditions so as to modulate the shrinkageprocess.

Essentially, shrinkage describes the extent to which the materialchanges in volume as it changes from a liquid to a solid. Inconventional injection molding, the molds are not temperature controlledwith pressure, so the molten polymers used by conventional methodscontract upon contact with the cold tool steel of the injection mold,and this causes shrinkage. In the present machines and systems,shrinkage may be controlled and typically is a non-issue due to thetemperature controlled pressurized mold which ensures the moltenbiopolymer fills the maximum surface area inside of the mold withoutpremature cooling, as well as the applied uniform stress of thepressurized mold cavity itself further aiding in this regard.

With regard to the production of light weight products as a generalrule, the more a polymer is expanded, the greater the reduction inweight. The present system, however, is configured for optimizing thesingle-phase solution by modulating the conditions via the applicationof appropriate pressure, temperature, and time, such that the optimumquality of a lightweighted foam can be achieved. This is good forproduct applications that require a lightweight foam, such as incushioning, footwear foams, and foams used to produce athleticequipment, for example. Likewise, with respect to controlling sink marksin conventional flexible foam manufacturing, sink marks and voids arecaused by localized shrinkage of the material at thick sections withoutsufficient compensation when the part is cooling.

Particularly, a sink mark typically occurs on a surface that is oppositeto and/or adjoining a leg or rib. This occurs because of unbalanced heatremoval and/or similar factors. After the material on the outside of thefoamed part has cooled and solidified, the core material starts to cool.Its shrinkage pulls the surface of the main wall inward, causing a sinkmark. If the skin is rigid enough, deformation of the skin may bereplaced by formation of a void in the core.

Unlike the sink mark and void challenges faced with conventionalflexible foam molding, the machine configuration and present systemparameters are controllable so as to produce a biodegradable andindustrially compostable flexible foam of the present disclosure thatminimizes the encountering of these issues. Particularly, in the presentprocess, the SCF gas is controlled in a manner so to modulate, e.g.,maximize, the cell structure of the polymer matrix within the foamingprocess. This maximization of the specialized foaming process betterensures that there are no undesirable sink marks or voids within thefinal foamed part.

Additionally, as indicated, a useful benefit of the present system isthat it utilizes low cost materials, and the produced end products haveless warping. Particularly, for many of the reasons discussed above, thepresent disclosure benefits from a process where the SCF gas isresponsible for maximizing the cell structure of the polymer matrixwithin the foaming process. This maximization of the specialized foamingprocess ensures that there is minimal warping within the final foamedpart.

Another benefit of the present system is that it may be configured so asto control tolerances. For instance, the system may be configured forperforming tight tolerance flexible foamed injection molding.Particularly, tight tolerance flexible foamed injection molding aspresented herein may be employed so as to produce parts that worktogether smoothly and contribute to an overall lower failure rate forthe product.

In order for a product to work reliably and as intended, all of itsparts must fit together smoothly. Accordingly, the present apparatusesand their component parts have been designed to tightly control thetolerances. Typically, these parts are produced with the best tolerancepossible. There are different ranges of acceptable tolerances; forexample, a very tight tolerance is +/−0.001″. Sometimes even a fewthousandths of an inch can mean the difference between a part that fitsand one that doesn't.

Consequently, it is useful to identify tight tolerances early in thedesign phase. This is because the design engineers must factor inrequirements for foamed part geometry, the overall foamed part size, andthe foamed part wall thickness—all of which have an influence ontolerance control, and all of which can exacerbate sink marks, warping,and inconsistent part tolerances if not carefully managed. The presentsystems and apparatuses overcomes most of these design challenges, whilestill using best design practices, as the SCF gas is responsible formaximizing the cell structure of the polymer matrix within the foamingprocess. Likewise, the system may be configured so as to cool morequickly within the molds.

As a result of the forgoing, sink marks, warping, and inconsistencies intolerance are greatly reduced. This is due in large part to theuniformly sized and evenly distributed microscopic cells within thefoamed matrix. Accordingly, in order to achieve these benefits themicrocellular foaming process should be finely controlled. For instance,as indicated, when foaming occurs along the melt front, advancement canintroduce streaks and flow marks on the molded surface thereby causingimperfections.

In addition to the above, these imperfections may be further minimizedherein by employing one or more of co-injection and in-mold decorationtechnologies. However, in many instances, this may be cost prohibitive.Nevertheless, the present system overcomes such cost prohibitiveinstances by selecting premium product opportunities where theadded-values of the present disclosure can be accepted and appreciated.

It is to be noted that in various instances there may be disadvantagesto SCF foaming, as in some instances, it can cause changes in meltviscosity and other physical properties. Particularly, when uniformlydiffusing SCF into a polymer melt, the single-phase solution, acts as areversible plasticizing agent by reducing the viscosity of the polymerby increasing the free volume. This effect also reduces the glasstransition temperature of polymers as well as the tensile strength ofthe same. This can lead to nonuniform bubble sizes.

Nonuniform bubble sizes potentially lead to the production of a moldedfoam part that has inconsistent technical performance propertiesthroughout the part and potentially non-desirable cosmetic issues aswell. These are both problems when attempting to produce a consistentlyreproducible biodegradable and industrially compostable flexible foamthat contains the same technical performance properties frompart-to-part in during mass production. The present system is configuredto overcome these difficulties.

Accordingly, as discussed above, to overcome these disadvantages, and tomore finely control the microcellular foaming process, the abovediscussed gas counter pressure (GCP) is employed. As discussed above,the gas counter pressure is finely controlled such that the gas bubblesare regulated from contacting and breaking through the surface of thefoaming material as the foamed part is formed. This is achieved by thecounteracting pressure being applied by the GCP system into the moldcavity, which may be at or around the same time that the moltensingle-phase solution is injected, while controlling the hold timewithin the mold. The mold temperature and pressure may also be finelycontrolled for these purposes.

Once injected, the inert gas bubbles are subjected to immense forces andtherefore the molten single-phase solution isn't given the opportunityto release the trapped bubbles to the outside of the foamed structurewhile being formed. Likewise, the immense forces being exerted on thesingle-phase solution help to better distribute the millions of tinybubbles within the foaming structure inside of the mold, as well as toassist with bubble size consistency. The result is a molded foam partwith cosmetically smooth skin formed on the outside of the part, and aconsistent bubble size for repeatable technical performance propertiesfrom part-to-part during mass production.

For instance, the system may be configured so as to allow theintroduction of GCP to control the foaming process, such as by applyingdifferent gas pressures and/or temperatures at the melt-injection stage.Consequently, GCP is introduced into the foaming process within the moldcavity that sits within the injection molding machine. First, an inertgas, is pumped by a gas compressor and gas pump into the mold cavitythrough a gas control valve. A gas pressure sensor feeds real-time datafrom the gas control value back to a computer-controller

The system initiates the GCP dosing into the mold cavity by setting thedosing parameters and hold times within the computer system. Thecomputer system then initiates the proper dosing of the inert GCP shotinto the mold cavity. Without the use of GCP, the biopolymer melt wouldenter the mold cavity and immediately begin to foam, generatingnonuniform bubbles of gas that break through the surface and createundesirable swirl marks on the exterior of the foam, which isproblematic.

Likewise, the injection speed may also be finely controlled, such aswhere the injection speed can be determined by the difference betweenthe screw pressure (Pscrew) and the gas pressure (Pgas). Specifically,when Pscrew is slightly higher than Pgas, and both parameters are highenough, the SCF-dissolved melt flows into the mold cavity withoutfoaming. Setting Pscrew higher than Pgas, and Pgas lower than thecritical pressure, results in partial foaming. Finally, the appropriatechoice of Pscrew, Pgas, and pressure difference combined with dynamicmold temperature enables more precise control of the bubble size.Accordingly, by fine tuning these parameters flow induced streaks can beminimized if not eliminated altogether.

Specifically, these parameters may be determined in part by aconsideration of the flow behavior. For instance, in one embodiment, arheological (flow) was produced with the behavior of a polymer melt thathas been dissolved with 0.4 wt % SCF of N2, under different moldtemperatures (185, 195, and 205 C, injection speeds (5, 10, and 15 mm/sscrew speed), and GCP's (50, 100, 200, and 300 bar). In such aninstance, the measured shear rate was within the 3000-11000 s-1 range,and the glass transition temperature, Tg, was reduced from 96 to 50 C,when the GCP was 300 bar. Likewise, in this instance, as compared withconventional injection molding, melt viscosity went down by about 30%when the GCP was increased from 50 to 200 bar.

Specifically, when the GCP is 300 bar, the viscosity of the single-phaseinjection melt without any foaming can be reduced by as much as 50%,depending on the injection conditions. This is useful because it lowersthe pressure requirements and temperature requirements, which therebyreduces manufacturing cost, specifically energy costs, and also reducesthe foamed parts cycle time during production. Consequently these systemparameters all for greater energy savings owing to lower pressure andtemperature requirements, and less cycle times, which translates to moreparts produced faster and for less money, such as by selecting the rightbiopolymer compound and tailoring the process temperatures, pressures,and hold times to fit the materials mechanical properties.

Additionally, as indicated, an important feature of the present machinesand systems is that they may be configured for controlling the bubblesize so as to be more uniform. As discussed above, this may beeffectuated in part by controlling the temperature, pressure, SCF dosingcontrol, GCP, DMTC, and other parameters discussed above. All of theseattributes work in concert to ensure the optimal, most uniform bubblesizes and their optimal homogeneous dispersion within the foamed matrix.Further, the surface quality may be improved by controlling the drift offluid along the melt front.

As its name suggests, the melt-front is the point at which the moltensingle-phase solution enters the molding cavity. The melt-front velocityis the melt-front advancement speed. For any mold that has a complexcavity geometry, part of the cavity may fill faster than other areas. Bycontrolling the melt-front velocity, such as by controlling thetemperature, pressure, and SCF dosing control, among controlling otherparameters, a more uniform mold cavity fill speed can be achieved, andthis ensures that the surface quality of the resulting foam part can becosmetically acceptable.

Accordingly, once the single-phase solution has been created, themodified injection molding machine, as described above, maintains thesolution in a pressurized state until the start of injection. Forinstance, the machine may be configured to achieve this through thecombined efforts of a shutoff nozzle and screw position control, asindicated above. Particularly, the shut-off nozzle may be configured soas to serve as the connection between the plasticizing barrel (withreciprocating screw) and the mold. Such shut-off nozzles can beself-controlled or externally controlled, and they may be used to avoiddrooling of the melt between molten shots and thus preventdepressurization and premature foaming into the mold.

Consequently, the shutoff nozzle prevents depressurization and prematurefoaming into the mold. For example, without a shutoff nozzle, thesingle-phase solution would not have sufficient pressure within the moldcavity and the desired molded foam part would not be produced. Likewise,either active or passive screw position control may be employed toprevent depressurization through the backward movement of the screw.

Particularly, the system may be configured so as to implement activescrew position control, such as where the position of the screw iscontinuously monitored, and the pressure applied to the back of thescrew is adjusted to maintain a determined position setpoint or aconstant pressure that is held on the back of the screw. For instance,in passive position control, the oil used to regulate back pressure isprevented from draining to its tank at the end of screw recovery. Thisresidual oil keeps the screw from moving backward due to the pressure ofthe single-phase solution.

Additionally, as indicated above, a proper mold design helps maintainthe single-phase solution. Specifically, in those instances, where amold includes a hot runner system, one or more valve gates may beincluded and controlled so as to prevent material dribbling from thenozzles, such as upon mold open. More particularly, a hot runner systemmay be used herein in the injection molding apparatus and may include asystem of parts that are physically heated such that they can be moreeffectively used to transfer molten plastic from the machine's nozzleinto the mold tool cavity. For instance, a “cold” or a “hot runner” canbe used, such as where a cold runner is an unheated, physical channelthat is employed to direct molten plastic into the mold cavity after itleaves the nozzle, and the hot runners are heated while cold runners arenot.

Likewise, in various instances, the apparatus may include a nozzle breakthat is configured to break contact with the sprue bushing during normaloperation. This configuration is useful in stack or tandem molds, thatemploy a shutoff on the sprue bushing. Particularly, the sprue bushingmay be configured to accept the machine nozzle and thereby allow formolten biopolymer compounds to enter the mold. In the event that themachine nozzle has to be disengaged from making contact with the spruebushing, the molten biopolymer compound may drool backwards from thesprue bushing and depressurization of the mold can occur. Any moltendrool waste can increase production costs, negatively affects the nextshot of the melt, and can even prevent proper closure of the mold whichwould potentially create even more problems.

To overcome this, selecting a sprue bushing with shutoff may beemployed. Otherwise, the pressure from the hot runner will be relievedthrough the sprue bushing. Particularly, when a sprue bushing requires ashutoff, the shutoff prevents the built-up in-mold pressure fromescaping in addition to the other benefits mentioned above. Anydepressurization of the mold would potentially prevent the foaming ofthe molten part and as a result, the desired molded part would not beformed.

As indicated above, a variety of foaming agents may be utilized forinjection molding of the biodegradable and industrially compostablemicrocellular foams. In particular instances, these foaming agents mayinclude inert and/or noble gases, such as inert nitrogen gas or carbondioxide or other gasses capable of being converted into a supercriticalfluid (SCF) state. In accordance with the apparatuses, systems, andtheir methods of use disclosed herein the SCF may be introduced, e.g.,injected, into the machinery, e.g., to the melt barrel such as through aspecially designed computer-controlled injector that may be coupled,e.g., affixed, to the injection molding machine barrel such as forfeeding the foaming agent into the molten biopolymer melt within thebarrel. The injection molding machine controller may be programmed todeliver a specific SCF gas dosing amount, whether nitrogen or carbondioxide or the like, into the biopolymer melt, which delivery may beoptimized by the system controller.

Consequently, each of the aforementioned SCF foaming agents has itsplace, depending on the technical requirements of the final part beingproduced. Particularly, as indicated, a useful SCF is carbon dioxide inits supercritical state is denser than nitrogen at the same pressure yethas a much higher heat capacity. Experiments have shown that carbondioxide in a supercritical state produces dense foams that may be usefulin certain cushioning applications. By contrast, supercritical nitrogencan be used to produce the low density foamed part with smaller cellsthat is useful for footwear and sporting goods applications of thepresent disclosure.

Accordingly, a useful foaming agent for producing athletic goods, suchas shoes, is SCF nitrogen gas as it provides improved weight reductionand a fine cell structure at much lower weight percentages than SCFcarbon dioxide, but for furniture and automotive uses, a useful foamingagent is carbon dioxide which produces a much larger cell structure,albeit at greater size and/or weight. Specifically, in variousinstances, enhanced weight reduction of foamed parts is a usefulcharacteristic for product applications requiring the least amount ofweight. As a non-limiting example, it is an ongoing need for runningshoes to contain flexible foams that are very lightweight and thatdemonstrate the ability to withstand repeated abuse.

By offering an enhanced weight reduction with fine cell structure in theaforementioned example, the injection molded flexible foam part would berelied upon for its ability to increase the runner's efficiency by wayof making an acceptably lightweight shoe. Moreover, the fine cellstructure of the aforementioned foam would ensure a very durable runningshoe having component parts that would be capable of handling repeatedimpact forces arising from the runner constantly applying pressure andimpact onto the foamed parts of the shoes while in acceleratedlocomotion.

In fact, SCF nitrogen levels will typically be at least 75 percent lowerthan the SCF carbon dioxide level required to achieve comparable parts.So being, the greatly reduced SCF nitrogen level requirements whencompared to SCF carbon dioxide ensures the optimal material savings andtime savings when mass producing the biodegradable and industriallycompostable flexible foams of the present disclosure as employed inmaking shoe components. SCF carbon dioxide, however, is a useful foamingagent in a variety of particular situations, such as when viscosityreduction is the primary processing goal, and/or when the applicationcan't tolerate SCF nitrogen's more aggressive foaming action.

In certain instances, SCF carbon dioxide is a suitable foaming agent,particularly in semi-flexible foams. Both flexible and semi-flexiblefoams can be included under the same category of flexible foams as theyboth are derived from polymers with a glass transition (Tg) below theirservice temperature, which is usually at room temperature. During thephysical foaming process with a physical blowing agent, a depression inthe glass transition is seen. These differences in the effectiveness ofnitrogen and carbon dioxide foaming agents stem from their behavior inthe biopolymer melt.

For instance, carbon dioxide, which becomes an SCF fluid at 31.1 Celsiusand 72.2 bar, is 4 to 5 times more soluble in biopolymers than nitrogen,which becomes a supercritical fluid at −147 Celsius and 34 bar. Forexample, the saturation point in an unfilled biopolymer is about 1.5 to2 percent by weight of nitrogen, depending on temperature and pressureconditions, while the saturation level of carbon dioxide is closer to 8percent by weight. Carbon dioxide also exhibits a greater mobility inthe biopolymer, allowing it to migrate further into existing bubblesthan nitrogen. From the perspective of cell nucleation, greatersolubility and mobility means fewer cells will be nucleated, and thosethat do nucleate will tend to be larger.

Solubility, however, becomes an advantage when the goal is viscosityreduction. An SCF dissolved in a biopolymer acts as a plasticizingagent, reducing the viscosity of the biopolymer. Because viscosityreduction is partly a function of the amount of SCF added to thebiopolymer and because carbon dioxide has a higher solubility limit thannitrogen, the ability to reduce viscosity with carbon dioxide isgreater. Carbon dioxide is also useful when the amount of nitrogenneeded to produce a part is so low that it is not possible toconsistently process parts.

Since carbon dioxide is a much less aggressive foaming agent, there aretimes where it is easier to run low levels of carbon dioxide. Forexample, 0.15 or 0.2 percent carbon dioxide as compared to very lowlevels of nitrogen at less than 0.05 percent. Instances as indicated inthe previous example occur primarily with soft materials and parts withthick cross-sections. Accordingly, the physical foaming agent, be it SCFnitrogen or SCF carbon dioxide or other SCF, play a useful role in thefinal foamed parts and the eventual products that will contain them.

Firstly, selecting the appropriate combination of compatible biopolymeror biopolymer compound and the associated SCF gas is useful. Secondly,properly utilizing the SCF gas by way of the optimal dosing weight andpressure is critical to ensuring the maximum saturation within thesingle-phase solution, and for ensuring the optimal generation of nucleifor producing millions of uniform bubbles within the foaming matrix.Additionally, the end result, a homogenously formed injection moldedflexible foamed part, relies upon all aspects of the SCF and GCP gasdosing process working symbiotically with the injection molding machinetemperature, pressure, and hold time for achieving commerciallyacceptable molded foamed parts, as explained above.

As indicated, in one aspect, a process of manufacturing biodegradableand industrially compostable flexible foams, whether open-cell orclosed-cell is provided. In various instances, the manufacturing processincludes one or more of the following steps. First, a thermoplasticbiopolymer may be blended into a masterbatch for foaming. As anon-limiting example, the referenced masterbatch may be produced by atwin screw extruder in which two or more biopolymers, fillers, and/oradditives may be homogenously blended into a single polymer melt, suchas within the extrusion barrel. The molten biopolymer blend is thenstrand-extruded, cooled, and pelletized into granules called amasterbatch, which may then be processed as described above. Anycombination of suitable biopolymers, bioplastics, fillers, additives,and colorants may be incorporated into the masterbatch production.Accordingly, once produced the thermoplastic biopolymer blend may beinjection molded into a suitable mold shape with a SCF, such as inertnitrogen or carbon dioxide gas.

As described above, the present Injection molding may be employed in amanufacturing process for producing parts by injecting molten materialinto a product mold. In the present disclosure, a suitable biopolymer orbiopolymer blended compound is selected, such as in granular form. Theaforementioned granules may be pre-dried in an auxiliary pellet drier toensure any latent moisture is removed. The pre-dried pellets may then beintroduced into the injection molding machine hopper. The operator thenselects the optimum barrel temperatures, nozzle temperature, and moldtemperatures of the injection molding machine, and inputs these valuesby computer-control.

Further, the optimal SCF gas dosing percentage and pressure as well asthe optimal GCP gas dosing and pressure may be scaled and these valuesmay be input into or be otherwise determined by the system control unit,e.g., dynamically. Once the system is properly configured, the injectionmolding machine is ready to operate. The granules may be released intothe screw and barrel of the injection molding machine in an amountspecified by computer control where they are melted at a specifictemperature or set of temperatures.

The SCF gas is introduced into the injection molding machine barrelthrough the SCF injector by computer control under controlled pressureand dose size. The SCF saturates the now molten granules and asingle-phase solution is generated. Then, with proper back pressure andscrew positioning, the injection molding machine sends a measured shotof single-phase solution into the dynamically temperature controlledmold cavity. Nuclei growth is experienced within the melt and millionsof microcellular bubbles are formed within the biopolymer melt.Substantially simultaneously, the GCP system sends a pre-metered dose ofcounter pressure gas into the mold by computer control that optimizesthe uniformity of the cells and conditions the surface texture for anoptimal cosmetic appearance. The dynamically temperature controlled moldtemperature may then be switched to water cooling and the formation ofthe bubbles and the expansion of the melt stops. At this point, theflexible foam molded part is now formed and it is ejected from the mold.

Particularly, as indicated above, the system may be configured so as toimplement dynamic mold temperature control, which may be used to produceoptimal cell structure. For instance, as described, dynamic moldtemperature control (DMTC) implements rapid electrical rod heating andrapid water cooling. More particularly, the DMTC procedure employedherein may include one or more of the following five main components: anair compressor, a valve-exchange device, a computer-controlled moldtemperature control unit, an electrically heated mold, and a coolingtower. The cooling tower is configured to provides water cooling to themold, for the performance of cooling operations, while a suitablyconfigured air compressor generates compressed air to drive gas throughpneumatic valves so as to exclude any residual cooling water fromentering the mold after cooling. One or more valve exchange devices maybe configured and employed to switch the valves to transfer differentmediums from the various machine pipelines to the mold, such as for hotand cold thermal cycling. An electrically controlled heating element maybe included and configured for molding the final shape of the foamedparts. Together the water tower and heating element may function so asto finely control the mold temperature so that the heating and coolingof the mold may be rapidly heated and/or cooled in performance of themolding process.

All of this is coordinated with the injection molding machine by thesuitably configured computer processor. For instance, a non-limitingexample of the cooling water temperature control of the DMTC system ofthe present invention may be 15 to 30° C., and a further non-limitingexample of the heating element temperature range of the DMTC system mayrange between 60° to 150° C., and may be in the range of 90° C. to 130°C., and may be any temperature there between. In these manners, thebiopolymer melt, pressure, and time may be controlled such that adesirable flexible foam is formed.

Particularly, during the injection molding process of the presentdisclosure, SCF is injected into the polymer melt. A single phase ofpolymer-SCF mixed solution is obtained under definite temperature andpressure within the injection molding machine screw and barrel. Thetemperature and pressure may be variably controllable bycomputer-control and relate directly to the type of flexible foam beingproduced and for what type of end product application. By applyingvarying screw-contained SCF single-phase solution pressures and GCPpressures, in concert with proper shot sizes, shot hold times, melttemperatures, and mold temperatures, an entire system is created bywhich high-quality and commercially acceptable biodegradable andindustrially compostable flexible foam parts may be produced, such as byutilizing gas counter pressure in the injection molding process so as toensure the optimal foam structure with the least amount of cosmeticdefects and little to no plastic skin on the outside of the foamed part.

As indicated, a useful benefit of the products produced in accordancewith the devices, systems, and their methods disclosed herein is thatthey may be biodegradable and/or compostable, such as in a home or anindustrial composting protocol. Particularly, producing goods that areconfigured for being decomposed in an industrial composting regimeensures that the flexible foam will last the usable life of theresulting product, such as by functionalizing it in a manner so that itdoes not breakdown or fall apart mid-use within the finished goods. Forexample, it would be detrimental for a person to purchase furniture, apair of shoes, or other athletic equipment that were made from theflexible foam of this disclosure only to have the foam degrade duringregular use before the end of the products usable life.3

More particularly, the present disclosure benefits from the use of aninert physical foaming agent and biodegradable and industriallycompostable biopolymers or biopolymer compounds. These two aspects cometogether to form a single-phase solution that is functionalized within aspecialized flexible foam injection molding system. The outcome isbiodegradable and industrially compostable flexible foams for use innumerous types of end-products; a non-limiting example of which isfootwear foams for use in making shoes. The resulting flexible foams arenon-crosslinked, chemical-free, and environmentally benign.

At the end of the biodegradable and industrially compostable flexiblefoams life, it can be redirected through waste-diversion to appropriateindustrial composting facilities whereby the foam is ground up andindustrially composted into useable biomass. The end result produces asystem by which aspects of the so-called circular economy are adheredto. The flexible foam of the present disclosure starts and ends as“dirt-to-dirt” meaning that the natural biological process has beenadapted to make materials and products for human use with the leastamount of environmental impact. These flexible foams do not compromiseon either technical performance properties during their useable life,nor on their environmentally conscious design.

As discussed herein above, the devices, systems, and their methods ofuse herein may be employed for the purpose of producing one or moremolded end products, such as for components for use in footwear,seating, automotive, protective gear, and/or sports gear. Accordingly,in various embodiments, provided herein is one or more components usefulin the construction of a shoe, such as a sole, midsole, and/or insolethereof, such as where the sole forms the base of the shoe, and isconfigured for making contact with the ground, the midsole forms anintermediate structural and cushioning element, and the insole isconfigured for being inserted within a shoe and thereby providingcushioning and/or support to the shoe.

In certain embodiments, the shoe component may include a foam materialproduced herein that may be environmentally friendly, bio-degradable,and compostable. In various instances, each individual component may becomposed of a plurality of layers including a base layer and acushioning layer, such as where the cushioning layer. For instance, inparticular embodiments, a support member such as a support member beingcoupled to the base layer may be included, and where the component is aninsole, at one or more of an arch contacting or heel contacting portionmay be included.

Particularly, in various embodiments, a foamed material may be producedsuch as where the foam materials may be used in the production ofcushions, cushioned furniture, shoe components, such as insoles thereof,mats, fibers, weaves, and the like. Other useful products may includecaulking, such as silicone caulking, silicone medical gloves, siliconetubing for drug delivery systems, silicone adhesives, siliconelubricants, silicone paints, and other suitable silicone products, e.g.,condoms. In various embodiments, the foam products may be produced in amanner where the foamed material may have one or more anti-microbial,anti-bacterial, anti-fungal, anti-viral, and/or anti-flammableproperties.

More particularly, in one aspect, this disclosure may be directedgenerally to a process for the manufacture of furniture, such asupholstered furniture and/or the cushions thereof, such as furniturethat includes or is otherwise comprised of foam, e.g., that isbiodegradable and/or compostable. Hence, the foams of the disclosure areadvantageous for use in the manufacture of furniture that includes suchproduced foam inserts. The resins and foams produced and employed haveproven to be advantageous for use as cushioning materials, such as forpillows, couches, beds, seat cushions, or for other upholsteringfurniture, and the like.

For instance, in accordance with the methods disclosed herein above, amold of a small to large block of foam can be produced, such as to forma foam insert, such as for use in furniture or car accessory components.The block foam may then be cut into smaller blocks of the desired sizeand shape, based on the type and form of the furniture being produced.Specifically, the sized and cut blocks may then be applied to orotherwise fit within the furniture or car frame or other boundingmaterial, together which may be covered to produce the final furnitureproduct, whether it be a pillow, sofa, a cushion, e.g., a sofa or carcushion, or the like. Additionally, where desired, an outer casing orbounding material may be attached to the frame material, such as bystapling, and/or tacking, or otherwise fastened to the frame of anarticle to be upholstered and covered with a fabric or other material.

Accordingly, in various embodiments, when manufacturing upholsteredfurniture, such as a couch or a car seat, a frame may be produced.Various internal, e.g., structural, components of the furniture may beinstalled within the frame, such as springs or the like, and then thefoamed sheets, produced in accordance with the methods disclosed hereinabove, may be positioned in, over, and around the springs, such as forcushioning and/or insulation. Of course, other materials may beincluded, such as layers of cotton, wool, felt, rubber-based products,and the like, and a cover material may then be added so as to cover theframe and finish the product manufacture.

Specifically, the present foams along with other materials disclosedherein may function as padding, or filling, which may be shaped,adjusted, and tucked beneath a cover as the cover material is stretchedover the frame. Additionally, as indicated, in various instances, thefoam products produced herein are useful in and above those known in theart for a number of reasons, not the least of which is the fact thattypical PU and/or EVA foams are not in any manner bio-degradable,whereas the component of the foams produced herein are. Hence, invarious embodiments, a method of constructing furniture upon an openframe is provided. For instance, in one instance, the method may includeone or more of the following steps.

Particularly, the method may include providing a frame, the framedefining back, a plurality of side walls, and seat portions, such aswhere the back frame portion is extended substantially vertically andthe seat portion extends substantially horizontally, relative to oneanother, in a manner such that the seat portion transects the verticalportion. The method may further include cutting a flat sheet of foam toappropriate size and shape to provide padding for the back and seatand/or side wall portions, cutting flat cover material to appropriatesize and shape to finish the back, seat, and/or side wall portions,attaching the foam sheets and the cover material together at spacedpositions and compressing the foam to form a contoured predetermineddesign in the outer surface thereof, and to form a substantially flatsub-assembly wherein the foam sheet and cover material are free forrelative movement intermediate the positions of attachment, and shapingand attaching the sub-assembly to the frame. The cover for the foamcushion or cushioned article can be any suitable covering materialordinarily used in upholstering furniture and covering ornamentalpillows and the like, such as woven woolen fabrics, woven nylon fabrics,or fabrics woven from other various synthetic fibers as well as suchmaterials as leather and the like.

Further, in another aspect, this disclosure is directed generally to aprocess for the manufacture of shoe components, such as soles, midsoles,and/or the insoles of shoes, such as shoe components that include or areotherwise comprised of foam, e.g., compostable foam. Specifically, inparticular embodiments, methods for making soles, midsoles, insoles,and/or other shoe inserts are provided. For instance, the present shoeinsert may be a form of cushioning device that is adapted to be insertedor otherwise fit within a shoe, e.g., a running shoe or sneaker, whichmay be configured so as to reduce the impact of a foot hitting asurface, e.g., the ground while running or walking, thereby absorbingand/or attenuating shock to the foot.

Particularly, shoe sole components, including midsoles and inserts mayinclude of one or a multiplicity of layers. For instance, in someinstances, a base layer, a foam layer, and/or a fabric layer may beprovided. Specifically, a base layer of a relatively resilient material,and/or a foam layer, e.g., disposed over the base layer, and/or a fabriclayer disposed over the foam layer may be included. Accordingly, themethod may include integrally forming the base layer, the foam layer,and the fabric into a tri-laminate sheet. In various instances, asupport layer may be disposed at least a heel area, which support layermay be constructed of a rigid material, such as of higher density thanthat of the laminate. An adhesive, glue, or other attachment mechanismmay be provided and employed for attaching and forming the tri-laminatewith the support layer.

More particularly, in other instances, the method for making a shoecomponent, such as an insert, may include the steps of: providing a foamlayer and/or providing a fabric layer; heating the foam layer; joiningthe foam and fabric layers; providing a base layer, e.g., a base layerhaving a density that is the same, greater, or a lesser density as tothe foam layer; and heating at least one of the base layer and foamlayer so as to couple the base layer with the foam layer so as to form adual or trilaminate.

The methods may further include providing a pre-formed support member,such as an arch support and/or heel member, which members may have adensity substantially the same, or less, or greater than the density ofthe foam layer. In particular instances, the support member may beformed of a compressed foam material so as to obtain greater density,and thus greater rigidity in comparison to that of the foam layer.Additionally, a heat and/or pressure reactivatable adhesive may beapplied between the support and/or heel member and the laminate. Amolding pressure may then be applied to the composition so as to causethe forming and/or shaping of the trilaminate into the support and/orheel member so as to form an integral one-piece shoe insert, with thepre-formed heel member forming a rear portion and/or the support memberforming a mid-portion of the bottom surface of the finished shoe insert,e.g., at the mid and/or heel area thereof, and the base layer formingthe bottom surface of the finished shoe insert at the forward areathereof.

It is to be noted, however, that a support and/or heel member need notbe included, and in some instances, one or more of the laminatecomponents may be excluded or other laminate layers added. It is furtherto be noted that, in certain embodiments, the foam layer may be moreflexible and/or cushioning, e.g., having a greater duometer, than thebase layer, which in turn may be more flexible and/or cushioning, e.g.,having a greater duometer, than the support member. Hence, the moreflexible foam and base layers may be relatively resilient and conform inshape to the desired shoe size and configuration, whereas the supportlayer(s) may be relatively more rigid.

Particularly, as indicated, the foam layer and/or one or more of thesupport layers may be constructed of the herein disclosed biodegradableand/or environmentally friendly foam material. Specifically, the supportlayer may be of a denser foam thus making the support layer more rigid.Hence, in various embodiments, the foam layer may have a density ofabout 2 or about 3 or about 5 to about 10 lbs. per cubic ft. or more,such as a density in the range of between about 4-6 lbs. per cubic ft.Additionally, the foam layer may have thickness of ⅛″ + or −5%, such asin a range of thickness of about 3/32″- 5/32″.

Likewise, the base layer may also have a density of about 2 or about 3or about 5 to about 10 lbs. per cubic ft. or more, such as a density inthe range of between about 4-6 lbs. per cubic ft. The thickness of thebase layer may be on the order of about 5/16″+ or −10%. However, invarious instances, the thickness of the base layer may range from about¼″ or less to about 7/16″ in thickness. With regard to the supportlayer, which may be formed primarily at the arch and/or heel areas ofthe insert, which may also be made of the biodegradable and/orcompostable foam disclosed herein.

However, the support layer may be made by being compressed so that thefinal density is on the order of 22-23 lbs. per cubic ft. The fabriclayer may be constructed of any suitable material, for example, cotton,polyester, or a polypropylene knit. In various instances, the materialand foam layers may be laminated together by a flame laminationtechnique that employs an open flame which is directed to the foamlayer. The open flame generates sufficient heat on the surface to causemelting of the flat sheet foam layer. Once melted, the fabric layer maybe joined therewith and the two sandwiched together layers may be runbetween chilled rollers, while sufficient pressure is applied betweenthe rollers so that the two layers are joined together.

At this point in the process, these layers are still maintained in aflat sheet form. These integrated layers may then next joined, also byflame lamination, to the base layer. The previously integrated materialand foam layers may be joined to the support layer and thesemulti-laminated layers may then be run between chilled rollers. At thisstage of the process, these layers are still in flat sheet form. Thelayers thus laminated to this point are then ready for molding. This maybe performed by heating the laminated layers to a molding temperature ofapproximately 250 F, such as for a period of about 1 to about 5 minutesor more, e.g., about 225 seconds. This heats the previously laminatedlayers sufficiently to permit them to be inserted into a mold.

The following is a description of various implementations of the presentdisclosure which makes reference to the appended figures. Accordingly,in one aspect, a footwear component is provided. Particularly, asillustrated in FIG. 1, an embodiment of the present disclosure is afootwear component, namely a microcellular flexible foam shoe midsole100 that is made of a biodegradable and industrially compostablethermoplastic biopolymer blend 102.

Specifically, the biodegradable and industrially compostable injectionmolded microcellular flexible foam shoe midsole is made from one or moreof a biopolymer and a biopolymer blend, such as including athermoplastic biopolymer. Particularly, the thermoplastic biopolymer orbiopolymer blend used to manufacture the biodegradable and industriallycompostable injection molded microcellular flexible foams can beoptionally created from any number of aliphatic and aliphatic-aromaticco-polyesters, or the like.

A non-limiting example of a suitable biopolymers finding use inproducing the biopolymer or biopolymer blend consist of polylactic acid(PLA), poly(L-lactic acid) (PLLA), poly(butyleneadipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polycaprolactone (PCL),polybutylene succinate adipate (PBSA), polybutylene adipate (PBA), andthermoplastic starch (TPS). Additionally, hybrid biopolymer blends maybe utilized in the manufacture of the biodegradable and industriallycompostable injection molded microcellular flexible foams. Anon-limiting example of a hybrid biopolymer blend consists ofalgae-containing poly(butylene adipate-co-terephthalate) (PBAT).

In the provided example, the algae portion of the hybrid biopolymerconsists of any suitable species of algae in a dried powder form.Several non-limiting examples of suitable algae species includeblue-green algae, green algae, red algae, brown algae, and diatoms, andcombinations thereof. The aforementioned dried algae powder can betwin-screw extruded on standard equipment with the PBAT biopolymer suchthat the algae powder denatures into the polymer chain of the PBAT. Thisthereby forms a hybrid biopolymer for use in the manufacture of thebiodegradable and industrially compostable injection moldedmicrocellular flexible foams of the present disclosure

The produced foam products may include or otherwise incorporate a numberof the following ingredients: a filler powder and/or one or moreadditives. Particularly, depending on the application, additives may beutilized in the biopolymer formulations as well. For example, oligomericpoly(aspartic acid-co-lactide) (PAL) may be optionally compounded intomasterbatch for accelerating biodegradation. Additionally, fillers suchas precipitated calcium carbonate from aragonite, starches, or the likemay be utilized to reduce part cost while maintaining the renewable andbiodegradable integrity of the finished flexible foams.

Further, additional additives for use in the biopolymer formulations mayconsist of one or more of the following. Nucleating agents, such asmicro-lamellar talc or high aspect ratio oolitic aragonite, may beincluded. Such nucleating agents can greatly improve key properties ofthe resulting flexible foam by preventing cellular coalescence, loweringbulk density, and improving rebound resilience, among other beneficiallyenhanced attributes. Several non-limiting examples of nucleating agentsfor use in producing biodegradable and industrially compostableinjection molded microcellular flexible foams are micro-lamellar talcmarketed as Mistrocell® by Imerys Talc America Inc., Houston, Tex. andhigh aspect ratio oolitic aragonite marketed as OceanCal® by CalceanMinerals & Materials LLC, Gadsden, Ala.

Colorants, Dyes, and Pigments may also be included. For instance,various colorants such as dyes, pigments, or bio-pigments may beoptionally used in the biopolymer formulations of the present invention.Several non-limiting examples are natural pigments of plant origin thathave been tailor-made for biopolymer use, such as a wide range offeredby Treffert GmBH & Co. KG, Bingen am Rhein, Germany or those offered byHolland Colours Americas Inc., Richmond, Ind.

There exist a number of configurations and embodiments that may beemployed depending on: the desired physical properties, and the intendedend-use of the shoe midsole 100, be it for work, recreation, water-use,or the like, that should not be limited by these examples.

A suitable device of the system may be exemplified in FIG. 2 and may beemployed in the production of a foam material as disclosed herein above.For instance, in use, a biopolymer masterbatch 202 is fed into thehopper 204 of any suitable injection molding machine 206. The biopolymermasterbatch is liquified by heating while being transported through theinjection molding machine screw 208. The nitrogen or CO2 gas 210 isinjected into the biopolymer melt and mixed 212. Further, thebiopolymer-gas mixture is under pressure and is injected into theinjection molding tool 214. In concert with the biopolymer-gasinjection, the gas counter pressure system 216 sends a dose of meterednitrogen or CO2 gas 218 into the pressurized molding tool via the gascontrol value 220.

Shortly thereafter, the dynamic mold temperature control system (DMTC)222 is controlling and adjusting the temperature inside of the moldingtool 214. The molding tool 214 is then sufficiently cooled and theresulting biodegradable and industrially compostable injection moldedmicrocellular flexible foamed part is ejected from the injection moldingmachine.

FIG. 3 provides a flowchart to illustrate the method 300 of producing abiodegradable and industrially compostable injection moldedmicrocellular flexible foam. At 302 a biopolymer mixture is selected,and at 304 the mixture is drawn into the injection molding machinethrough the material hopper. At 306, the biopolymer mixture is liquifiedand homogenized while being transported through the injection moldingmachine screw. At 308, the nitrogen or CO2 gas is injected into thebiopolymer melt. At 310, the biopolymer-gas mixture is under pressureand injected into the injection molding tool. At 312, the injectionmolding tool temperature is dynamically controlled to ensure the optimalcell structure. At 314, the optimal dose of gas counter pressure isapplied to the injection molding tool for a sufficient amount of time toensure the ideal foam structure with minimal skin thickness. At 316, theinjection molding tool is sufficiently cooled and the resulting moldedfoam part is ejected from the injection molding machine.

In some implementations, and without imparting limitations to thedisclosure herein, a biodegradable and industrially compostable flexiblefoam manufacturing process includes the steps outlined below. Processset-up procedures revolve around establishing a controlled SCF dosinginto the injection barrel: under screw speed, temperature, and pressureconditions that result in a single-phase solution.

Ensuring that the basic conditions of SCF dosing are met, there areprimarily seven process setpoints to adjust: SCF Delivery Pressure:Setting the bioplastic pressure against which the SCF is dosing duringscrew rotation. This refers to both the specific biopolymer backpressure during screw recovery and also to screw position control duringscrew idle. As a non-limiting example, pressure setpoints for thebiopolymer delivery could be in the range of 2,000 psi and 3,000 psi,and more preferably in the range of 2,700 psi and 2,800 psi. Thissetpoint sets the screw position at which the SCF dosing starts, whichcan then set the SCF injector to the open or closed position. Theposition should be set so that the pressure in the barrel during screwrecovery has become stable prior to the start of dosing. As anon-limiting example, the open position could be in the range of 0.3 and0.4 inches.

The percentage of the shot size and SCF may also be controlled. Thiscontrols the actual mass of SCF dosed during each cycle. As anon-limiting example, the shot size could be in the range of 100 gramsto 300 grams, and more preferably 200 grams. A non-limiting example ofthe SCF percent could be in the range of 0.45% and 0.75%, and morepreferably 0.5%. The system may also be configured for optimizingdosing. This is accomplished by maximizing the dosing time andminimizing the flow rate (pressure difference between the pre-meteringpressure and the delivery pressure). A non-limiting example of thedosing time is between 1-2 seconds, and more preferably 1.7 seconds.

A dynamic mold temperature control (DMTC) may also be implemented. Thisis a process that involves the rapid changing and controlling of themold temperature during the injection filling stage so as to therebydynamically control the mold temperature in terms of both hot and coldthermal cycling. Before the melt injection, the mold is first heated toa preset upper limit. During the melt filling stage, the temperature ofthe mold cavity surface is kept higher than the upper limit to preventthe melt from solidifying prematurely.

When the melt filling process has ended, the mold is cooled quickly to alower limit known as the ejection temperature, which is the temperaturethat the part is ejected out the mold cavity. A non-limiting example ofthe optimal mold temperature range of the present disclosure is between40° C. and 150° C. with a cooling speed of between 1° C. per second and15° C. per second, and more preferably 11° C. per second. A non-limitingexample of the mold cooling time of the present invention is between 80seconds and 100 seconds.

Likewise, the gas counter pressure (GCP) may also be controlled. This isa process that includes a pressurized mold cavity that is injected withnitrogen gas to counteract the expansion of the gas within the melt. Asthe counter pressure is released, the gas bubbles that wouldconventionally breakthrough the surface are trapped inside, creating asmooth skin. The GCP controls the foaming through surface quality, foamstructure, and skin thickness. A non-limiting example of gas counterpressure of the present invention is 0 bar/10 bar/30 bar/50 bar with aholding time of between 1 second and 25 seconds, and more preferably 5seconds. A non-limiting example of the average microcellular celldiameter of the present invention can be measured in micrometers (μm)between 1-micrometer and 100-micrometers, and more preferably40-micrometers.

In view of the above, in some implementations, a suitable thermoplasticbiopolymer blend is produced. Once the thermoplastic blend is produced,the thermoplastic biopolymer blend may be injection molded into asuitable mold shape, such as with the addition of an inert gas, such asnitrogen gas. Additionally, pressure may be finely controlled as well.

For instance, utilizing gas counter pressure in the injection moldingprocess may be implemented. This is also useful for further ensuring theoptimal foam structure with the least amount of cosmetic defects, andlittle to no plastic skin on the outside of the foamed part, which isimportant in making a foamed product that may have a multiplity of finaluses, based on the mold shape. The molding process may include theimplementation of a dynamic mold temperature control. For example, invarious embodiments, dynamically controlling the temperature of themolding process is useful for achieving optimal cell structure. Otherelements of the molding process that can be controlled includecontrolling: the biopolymer melt, the pressure, and time, such that adesirable flexible foam is formed.

Accordingly, in view of the above, the present disclosure relates to aprocess for injection molded microcellular foaming various flexible foamcompositions from biodegradable and industrially compostable bio-derivedthermoplastic resins for use in, for example, footwear components,seating components, protective gear components, and watersportaccessories.

Creating a biodegradable and industrially compostable microcellularflexible foam structure begins with a suitable biopolymer or biopolymerblend such as those of aliphatic and aliphatic-aromatic co-polyesterorigin. A non-limiting example of a suitable biopolymer blend ispolylactic acid (PLA) and poly(butylene adipate-co-terephthalate)(PBAT). The aforementioned blended thermoplastic biopolymer resins haveshown advantageous technical properties in forming the optimalmicrocellular flexible foam structure of the invention. Some of theenhanced technical properties include acceptable aging properties,excellent elongation, and exceptional compression set, among otherbenefits.

The optimal aliphatic and aliphatic-aromatic co-polyester biopolymers orbiopolymer blends alone cannot produce a flexible foam without asuitable foaming agent and foaming process. The most widely knownfoaming agent in use today is a chemical called azodicarbonamide (ADA).Azodicarbonamide is typically pre-impregnated into petrochemicalthermoplastic masterbatch resins for use in conventional injectionmolding foam processes. Unfortunately, ADA is not environmentallyfriendly, and it is a suspected carcinogen to human health. Moreover,conventional petrochemical thermoplastic masterbatch resins are notbiodegradable nor industrially compostable. To achieve the most optimalbiodegradable and industrially compostable flexible foam for theaforementioned invention, inert nitrogen gas or carbon dioxide in asupercritical fluid state is used as a physical foaming agent in amodified injection molding process. A modified physical foaming processis employed in concert with a suitable thermoplastic biopolymer orblended biopolymer masterbatch such that the biopolymer or biopolymerblend and foaming agent work harmoniously for producing the most optimalbiodegradable and industrially compostable flexible foams.

The injection molded process of this disclosure relies upon thehomogeneous cell nucleation that occurs when a single-phase solution ofbiopolymer or biopolymer blend and supercritical fluid (SCF) passesthrough the injection gate into the mold cavity. As the solution entersthe mold, the pressure drops which causes the SCF to come out ofsolution creating cell nuclei. The cells then grow until the materialfills the mold, and the expansion capabilities of the SCF are expended.This manufacturing process runs on injection molding machines that havebeen modified to allow the metering, delivery, and mixing of the SCFinto the biopolymer to create the single-phase solution. Dynamic moldtemperature control (DMTC) is employed to ensure consistent cellstructure within the expanding biopolymer melt. DMTC can best bedescribed as the rapid changing and controlling of the mold temperatureduring the injection filling stage; this thereby dynamically controlsthe mold temperature in terms of both hot and cold thermal cycling. Gascounter pressure (GCP) is also utilized in the manufacturing process toensure the optimal foam structure with little to no skin on theresulting flexible foam. GCP can best be described as a process thatincludes a pressurized mold cavity that is injected with SCF tocounteract the expansion of the gas within the melt. As the counterpressure is released, the gas bubbles that would conventionallybreakthrough the surface are trapped inside, creating a smooth skin. TheGCP controls the foaming through surface quality, foam structure, andskin thickness.

The creation of the single-phase solution, in which the SCF is fullydissolved and uniformly dispersed in the molten biopolymer, takes placeinside the injection barrel under carefully controlled processconditions: The SCF must be accurately mass flow metered into thebiopolymer for a fixed amount of time. And during the dosing period, theright conditions of temperature, pressure and shear may be establishedwithin the barrel. Back-pressure, screw-speed and barrel-temperaturecontrol, as well as the SCF delivery system all play a role inestablishing the process conditions that create the single-phasesolution.

Once the single-phase solution has been created, a modified injectionmolding machine maintains the solution in a pressurized state until thestart of injection. The machine achieves this through the combinedefforts of a shutoff nozzle and screw position control. The shutoffnozzle prevents depressurization and premature foaming into the mold.Either active or passive screw position control preventsdepressurization through the backward movement of the screw. Duringactive screw position control, the position of the screw is continuouslymonitored, and the pressure applied to the back of the screw is adjustedto maintain a position setpoint or a constant pressure is held on theback of the screw. In passive position control, the oil used to regulateback pressure is prevented from draining to its tank at the end of screwrecovery. This residual oil keeps the screw from moving backward due tothe pressure of the single-phase solution.

Proper mold design also helps maintain the single-phase solution. Moldswith a hot runner system require valve gates to prevent materialdribbling from the nozzles upon mold open. Molds in which the machinenozzle breaks contact with the sprue bushing during normal operation,such as with stack or tandem molds, require a shutoff on the spruebushing. Otherwise, the pressure from the hot runner will be relievedthrough the sprue bushing.

The foaming agent utilized for injection molding the biodegradable andindustrially compostable microcellular foams is either inert nitrogengas or carbon dioxide in a supercritical fluid (SCF) state. Each of theaforementioned foaming agents has its place, depending on the technicalrequirements of the final part being produced.

A useful foaming agent for this invention is SCF nitrogen gas as itprovides improved weight reduction and a fine cell structure at muchlower weight percentages than SCF carbon dioxide. In fact, SCF nitrogenlevels will typically be at least 75 percent lower than the SCF carbondioxide level required to achieve comparable parts. SCF carbon dioxide,however, is the preferred foaming agent in two situations: whenviscosity reduction is the primary processing goal or when theapplication can't tolerate SCF nitrogen's more aggressive foamingaction.

Differences in the effectiveness of two foaming agents stem from theirbehavior in the biopolymer melt. Carbon dioxide, which becomes an SCFfluid at 31.1 Celsius and 72.2 bar, is 4 to 5 times more soluble inbiopolymers than nitrogen, which becomes a supercritical fluid at −147Celsius and 34 bar. For example, the saturation point in an unfilledbiopolymer is about 1.5 to 2 percent by weight of nitrogen, depending ontemperature and pressure conditions, while the saturation level ofcarbon dioxide is closer to 8 percent by weight. Carbon dioxide alsoexhibits a greater mobility in the biopolymer, allowing it to migratefurther into existing bubbles than nitrogen. From the perspective ofcell nucleation, greater solubility and mobility means fewer cells willbe nucleated, and those that do nucleate will tend to be larger.

Solubility, however, becomes an advantage when the goal is viscosityreduction. An SCF dissolved in a biopolymer acts as a plasticizingagent, reducing the viscosity of the biopolymer. Because viscosityreduction is partly a function of the amount of SCF added to thebiopolymer and because carbon dioxide has a higher solubility limit thannitrogen, the ability to reduce viscosity with carbon dioxide isgreater.

Carbon dioxide is also preferred when the amount of nitrogen needed toproduce a part is so low that it is not possible to consistently processparts. Since carbon dioxide is a much less aggressive foaming agent,there are times where it is easier to run low levels of carbon dioxide.For example, 0.15 or 0.2 percent carbon dioxide as compared to very lowlevels of nitrogen at less than 0.05 percent. Instances as indicated inthe previous example occur primarily with soft materials and parts withthick cross sections.

Recyclable Injection Molded Microcellular Flexible Foams and a Method ofMaking the Same

FIGS. 4 and 6 illustrate a recyclable injection molded microcellularflexible foam 402 and a method of making the same in accordance with thepresent disclosure. Referring to FIG. 4, the foam 402 is preferably aclosed-cell foam but can also potentially be formed as an open-cellfoam. In various implementations, the foam 402 can be made to haveproperties and characteristics that are at least approximately similarto those of conventional non-recyclable ethylene vinyl acetate (EVA)foam or the like.

As discussed in greater detail below, the recyclable foam 402 is made byprocessing a thermoplastic polymer using an injection molding machineillustrated in FIG. 5. The thermoplastic polymer used to manufacture therecyclable flexible foam 402 can be optionally created from any numberof polyamide based thermoplastic polymers, polyamide copolymers, or thelike. A non-limiting example of suitable polymers finding use in thisinvention consist of polyamide 6, polyamide 6/6-6, polyamide 12.Alternatively, the thermoplastic polymer may comprise any number ofpolyamide block copolymers such as polyether-block-amide (PEBA), PAE,TPA, TPE-A, COPA, or the like. Other non-limiting examples of suitablepolymers and copolymers include polyamide 66 copolymer marketed underthe trade name of Vydyne by Ascend Performance Materials, LLC, Houston,Tex. The aforementioned thermoplastic polymer resin has shownadvantageous technical properties in forming the optimal microcellularflexible foam structure of the invention. Some of the enhanced technicalproperties include exceptional aging properties, excellent elongation,tensile strength, and compression set, among other benefits.

Additionally, blends of two or more thermoplastic polymers provide acombination of properties and price not found in a single thermoplasticpolymer. There are a number of ways to blend thermoplastic polymerstogether successfully. As discussed in greater detail below, twin-screwextrusion to melt two or more thermoplastic polymer together and to thenextrude the molten polymer resin blend into a strand that is cooled andfed into a pelletizer for producing an array of pelletized pieces calleda masterbatch. Another method of polymer resin blending is to usecompatibilizing agents to join unlike chemistries together in a polymerblend. Commonly, this too uses twin-screw extrusion or the like to meltthe compatibilizer and two or more polymers together in the non-limitingthermoplastic polymer types that are described above.

In one embodiment, the thermoplastic polymer comprises at least onemonomer or polymer derived from a post-consumer or post-industrialrecycled feedstock. For example, the thermoplastic polymer may comprisecaprolactam, recycled polyether block amide polymer, or the like. By wayof illustration, caprolactam may be derived from recycled feedstocks bydepolymerizing post-industrial or post-consumer material containingpolyamide such as fishing nets, carpet fibers, or industrial waste. Anon-limiting example of depolymerized post-consumer or post-industrialrecycled caprolactam include ECONYL® caprolactam, whether in flake,liquid or molten, provided by Aquafil USA Inc., Cartersville, Ga. Thethermoplastic polymer may additionally or alternatively comprise apolyamide polymer derived from post-industrial or post-consumerpolyamide carpet fiber that is collected, sorted, melted down, andreprocessed. One such polyamide polymer derived from post-industrialcarpet fiber is Econyl manufactured by the Aquafil USA Inc.,Cartersville, Ga. Additionally, polyamide waste, may be collected fromin or around the world's oceans in the form of fishing nets, or thatlike that can then be sorted, melted down, and reprocessed into upcycledusable polyamide material. An exemplary polyamide polymer derived fromcollected post-industrial fishing nets is Akulon Repurposed manufacturedby Koninklijke DSM N.V., Heerlen, the Netherlands.

Depending on the application, additives may be utilized in the polymerformulations as well. For example, fillers such as precipitated calciumcarbonate, oolitic aragonite, starches, biomass, or the like may beutilized to reduce part cost while maintaining the recyclable integrityof the finished flexible foams.

Further, additives for use in the polymer formulations may consist ofone or more of the following. Nucleating agents, such as micro-lamellartalc or high aspect ratio oolitic aragonite, may be included. Suchnucleating agents can greatly improve key properties of the resultingflexible foam by preventing cellular coalescence, lowering bulk density,and improving rebound resilience, among other beneficially enhancedattributes. Several non-limiting examples of nucleating agents for usein producing recyclable injection molded microcellular flexible foamsare micro-lamellar talc marketed as Mistrocell® by Imerys Talc AmericaInc., Houston, Tex. and high aspect ratio oolitic aragonite marketed asOceanCal® by Calcean Minerals & Materials LLC, Gadsden, Ala.

Colorants, Dyes, and Pigments may also be included. For instance,various colorants such as dyes, pigments, or pigments may be optionallyused in the polymer formulations of the present invention. Severalnon-limiting examples are pigments that have been tailor-made forspecific types of thermoplastic polymer use, such as a wide rangeoffered by Treffert GmBH & Co. KG, Bingen am Rhein, Germany or thoseoffered by Holland Colours Americas Inc., Richmond, Ind.

Use of recycled feedstocks to create a microcellular flexible foamdecreases the environmental impact that is typically associated withcreation of expanded thermoplastic polymer foams by sourcing sustainablematerials. As discussed in greater detail below, the method for creatinga microcellular flexible foam of the present disclosure augments theenvironmental benefits of using recycled feedstocks because theresulting products may be further recycled into thermoplastic polymerswhich may be subsequently utilized to create a new product frommicrocellular flexible foam or alternatively other products utilizingthermoplastic polymers.

The Method of Making a Flexible Foam

FIGS. 5 and 6 illustrate an injection molding machine 506 and method 600for manufacturing the recycled flexible foam 402 shown in FIG. 4. Hence,in one aspect the present disclosure is directed to a method of foaminga thermoplastic polymer. As described in greater detail below, themethod may be utilized to create any of a number of end products fromthe foam 402 such as technical athletic gear including shoe components,and other products where features such as cushioning, impact protection,comfort, and others are desired.

As shown in FIG. 5, the injection molding apparatus 506 includes ahopper 504 configured for receiving and introducing a plurality ofthermoplastic polymers 502 into the molding apparatus 506. A barrel 507is connected to the hopper 504 and configured for receiving thethermoplastic polymer 502 and including a specialized reciprocatingscrew-type plunger 508. The barrel 507 also includes a temperaturecontrol unit (not shown) to heat and cool the contents of the barrel507. As shown in FIG. 5, a computer controller 503 having a temperatureand pressure measuring device 505 is configured to sense temperature andpressure within the barrel 507. A gas dosing system 509 is fluidlyconnected to barrel 507 and includes a metering unit 512 configured forreceiving and introducing a fluid 510 into the barrel 507. The gasdosing system 509 maintains the fluid 510 above the critical temperatureand pressure (Tc and Pc, respectively) to create a super critical fluid(SCF) 510. In the method of the current disclosure, the SCF 510 is usedas a physical foaming agent that replaces chemical foaming agentsutilized in conventional methods of flexible foam production such asazodicarbonamide (ADA). By way of example, the SCF 510 may comprise aninert or noble gas such as nitrogen, carbon dioxide, helium, neon,argon, or xenon. Not only does the method of the present disclosureimprove the environmental impact in comparison with conventionalflexible foam molding methods by eliminating the environmentally harmfuland suspected carcinogen ADA from the process and replacing it with aninert or noble SCF, but, as will be discussed in further detail below,the flexible foam 402 of the present disclosure may be recycled at theend of their useful life as a result of the method described herein.

Referring to FIG. 6, the method for manufacturing a recyclable flexiblefoam 102 may begin with step 602: selecting the thermoplastic polymer502 and supplying the thermoplastic polymer 502 to the hopper 504 of theinjection molding machine 506. Subsequently, in step 604, thethermoplastic polymer 502 is then fed from the hopper 504 into thebarrel 507 and heated. In step 606, the heated barrel 507 melts thethermoplastic polymer 502 as the screw-type plunger 508 moves thethermoplastic polymer 502 through the injection molding machine 506.Further, the controller 503 may be configured to control and modulatethe screw-speed.

In step 608, the SCF 510 is introduced into the barrel 507 through aninjector 511 via the metering unit 512 connected to the injectionmolding apparatus 506, and the SCF 510 solubilizes in the meltedthermoplastic polymer 502 to create the single phase solution. The SCF510 can be adjusted in concentration within the melt, which influencesthe degree of foaming attained. Referring to FIG. 5, the metering system512 is configured for dosing the SCF at the appropriate amount into themelted thermoplastic polymer 502. A non-limiting example of the initialSCF gas concentration may be Co=0.25% with a melt temperature range ofbetween 176° C. and 250° C., and more preferably in the range of 180° C.Further, the controller 503 controls the pressure the SCF 510 isintroduced into the barrel 507 through the SCF injector. The SCF 510saturates the molten thermoplastic polymer 502 generating thesingle-phase solution is generated. Further, the screw-type plunger 508rotates within the barrel 507 at a speed necessary to homogenize thethermoplastic polymer 502 and SCF 510 and create a single phasesolution. The screw 508 may rotate within the barrel 507 between 1 to200 rpm, and preferably, from approximately 20 rpm to approximately 60rpm.

With respect to saturation, the injection molding machine 506 isconfigured for delivering a gas to the barrel 507 under a temperatureand a pressure to saturate the melted thermoplastic polymer 502 duringscrew rotation. Specifically, the controller 503 is configured tocontrol a combination of SCF delivery pressure and the SCF dose weight.The SCF pressure and dose may be controlled in a manner so as to affectthe single-phase solution. That is, the smaller the SCF dose, the lessSCF saturation need be within the biopolymer melt, whereas the largerthe SCF does, the more SCF saturation need be within the melt. Likewise,the lower the SCF delivery pressure, the lower the uptake of thesaturation, and therefore the lower the growth of nuclei that can growto form bubbles within the molten biopolymer melt. Moreover, the greaterthe SCF delivery pressure, the greater the uptake of the saturation, andtherefore, the greater the growth of the nuclei that can grow to formbubbles within the molten melt.

The controller 503 variably controls the temperature and pressure in amanner that is dependent upon the type of flexible foam being producedand for what type of end-product is being produced. Specifically, thetemperature throughout the system, such as within the barrel 507, may becontrolled so as to be between 100° C. and 600° C., such as between 200°C. and 500° C., for instance, between 300° C. and 400° C., and moreparticularly, between the ranges of 320° C. and 380° C., includingbetween 360° C. and 380° C. within the barrel. Likewise, the SCFdelivery pressure may be finely controlled so as to be in a range ofbetween 1,000 and 8,000 PSI, such as between 1,500 and 6,000 PSI, forinstance, between 2,000 and 5,500 PSI, particularly, between 3,000 and4,000 PSI, and more particularly between the ranges of 2,600 and 2,800PSI.

In the embodiment illustrated in FIG. 5, the controller 503 determinesand controls the SCF 510 concentration using a sensor that determinesthe amount of saturation and evaluates saturation process progressionand modulates pressure and temperature. The SCF 510 controllablysaturates the melted thermoplastic polymer 502 during rotation of thereciprocating screw 508 to create the single-phase solution underdefinite temperature and pressure. SCF is one part of a two-part moltenthermoplastic polymer compound mixture and it is used as a physicalblowing agent in the presence of definite pressure and temperature inthe present injection mold.

As discussed in greater detail below, the SCF 510 foaming agent may beselected from the list of noble and inert fluids enumerated above basedon the technical requirements of the final flexible foam 402 product.For example, carbon dioxide in its supercritical state is denser thannitrogen at the same pressure yet has a higher heat capacity. Carbondioxide in a supercritical state produces dense foams that may be usefulin certain cushioning applications. By contrast, supercritical nitrogencan be used to produce the low density foamed part with smaller nucleithat may be used when creating a foam 402 for footwear and sportinggoods.

Solubility, however, becomes an advantage when the goal is viscosityreduction. An SCF dissolved in a recyclable thermoplastic polymer 502acts as a plasticizing agent, reducing the viscosity of thethermoplastic polymer 502. Because viscosity reduction is partly afunction of the amount of SCF added to the recyclable thermoplasticpolymer 502 and because carbon dioxide has a higher solubility limitthan nitrogen, the ability to reduce viscosity with carbon dioxide isgreater. Carbon dioxide is also useful when the amount of nitrogenneeded to produce a part is so low that it is not possible toconsistently process the end product.

Since carbon dioxide is a less aggressive foaming agent, there are timeswhere it is easier to run low levels of carbon dioxide. For example,0.15 or 0.2 percent carbon dioxide as compared to very low levels ofnitrogen at less than 0.05 percent. Instances as indicated in theprevious example occur primarily with soft materials and parts withthick cross-sections. Accordingly, whether it is nitrogen, carbondioxide, or one of the other inert and noble gases enumerated above, thephysical foaming agent plays a useful role in the final foamed parts andthe eventual products that will contain them.

Selecting the appropriate combination of compatible thermoplasticpolymer or thermoplastic polymer compound and the associated SCF gas isuseful. Secondly, properly utilizing the SCF gas by way of the optimaldosing weight and pressure provides the preferred level of saturationwithin the single-phase solution, and impacts generation of nuclei(production of numerous uniform bubbles within the foaming matrix aswill be described in greater detail below). Additionally, the endresult, a homogenously formed injection molded flexible foamed part,relies upon all aspects of the SCF gas dosing process and the use of gascounter pressure working symbiotically with the injection moldingmachine temperature, pressure, and hold time for achieving commerciallyacceptable molded foamed parts.

Referring to FIG. 5, the reciprocating screw 508 is further configuredto compress and move the melted thermoplastic polymer 502 within thecavity of the barrel 507. A gas counter pressure (GCP) system 516 isconfigured for delivering a gas counter pressure to the barrel 507 so asto control expansion of the melted thermoplastic polymer 502. In theembodiment illustrated in FIG. 5, the GCP system 516 includes a gas pump515, a gas reservoir 518 including an inert gas such as nitrogen orcarbon dioxide, a compressor 517, a pressure sensor 519, and a gascontrol valve 520. The reciprocating screw-type plunger 508 and barrel507 are also configured to provide back pressure and deliver thethermoplastic polymer 502 into a mold 514 having a cavity is disposed influid communication with the barrel 507, and configured to receive themelted thermoplastic polymer 502 (described in greater detail below). Inthe embodiment shown in FIG. 5, the screw-type plunger 508 and barrel507 are configured to apply between approximately 2,000 psi andapproximately 3,000 psi, and more preferably in the range of 2,700 psiand 2,800 psi. The configuration of the screw-type plunger 508 andbarrel 507 also sets the position at which the SCF 510 dosing starts,which can then set the SCF injector to an open or closed position. Theposition should be set so that the pressure in the barrel during screwrecovery becomes stable prior to the start of SCF 510 dosing. As anon-limiting example, the open position could be in the range of 0.3 and0.4 inches.

In addition to the GCP system, the injection molding machine 506illustrated in FIG. 5 includes a dynamic mold temperature control (DMTC)522 configured to control the temperature within the mold 514. The DMTC522 may be employed in concert with the GCP system 516 to ensureconsistent cell structure within the expanding thermoplastic polymer502. The DMTC 522 may be configured so as to influence the rapidchanging and controlling of the mold temperature and/or pressure duringthe injection filling stage, and dynamically control the moldtemperature and/or pressure through use of hot and cold thermal cycling,with or without counter pressure.

With continued reference to FIG. 5, the controller 503 is configured soas to control the mold 514 temperature during the injection stage 610via the DMTC 522. More particularly, compared with conventionally knowninjection molding processes, an important characteristic of the dynamicmold temperature control employed herein is that the mold temperatureitself may be dynamically controlled. The DMTC 522 illustrated in FIG. 5utilizes rapid electrical rod heating and rapid water cooling.Specifically, the DMTC 522 includes five main components: an aircompressor (not shown), a valve-exchange device 526, acomputer-controlled mold temperature control unit (disposed within thecontroller 503), an electrical heating rod (disposed within the mold514), and a cooling tower 532. The cooling tower 532 may be used tosupply sufficient water cooling to the mold. The air compressor is usedto produce compressed air as the driving gas of pneumatic valves and toexclude residual cooling water from entering the mold after cooling. Inthe embodiment shown in FIG. 5, a water heating unit 534 is alsoincluded, and the valve exchange device 526 is used to switch the valvesto transfer different mediums from pipelines to the mold 514, providinghot and cold thermal cycling. For instance, the DMTC 522 may providewater cooling in the range of between approximately 15° C. andapproximately 30° C., and the electrical heating rod may heat the moldto between approximately 60° C. and approximately 150° C., and mayoptimally heat the mold in the range of 90° C. to 130° C.

The injection molding machine 506 depicted in FIG. 5 include pipes andother conduits for passing of reacting materials, which conduits areassociated with one or more heat exchange units, so as to heat and/orcool the reactants as they are pumped into and/or through the conduitsand pipes. In such an instance, the exchanger may be controlled toadjust the temperature to the reactive level. On one end of the pipe adispensing head may be included, which may be associated with one ormore valves. Further, the dispensing head may be hooked up to aprocessing line. The electrically heated mold is used for molding thefinal shape of the foamed parts. The function of the mold temperaturecontrol is to control the heating and cooling of the mold; all of thisis coordinated with the injection molding machine by computer-control.

Accordingly, as implemented herein, the controller 503 implements gascounter pressure to improve the control of the foaming process byapplying different gas pressures at the injection stage as describedbelow. The controller 503 is configured to manipulate the GCP system 516and DMTC 522 to regulate the temperature and pressure and therebycontrol nucleation and the resulting bubbles within the meltedthermoplastic polymer 502 and resulting foaming matrix.

As illustrated in FIG. 6, in step 610 the thermoplastic plunger 508advances forcing the melted thermoplastic polymer 502 through a nozzle(not shown) that rests against and which injects the thermoplasticpolymer 502 into the mold 514. The injection molding machine 506 sends ameasured shot of single-phase thermoplastic polymer 502 into thedynamically temperature controlled mold cavity 514. Prior to theinjection step 610, the DMTC 522 heats the mold 514 to a preset upperlimit. During the injection step 610, the DMTC 522 maintains thetemperature of the mold cavity 514 higher than the upper limit toprevent the melted thermoplastic elastomer 502 from solidifyingprematurely. The GCP system 516 delivers a gas counter pressure withinthe mold 514 to control nuclei growth, preventing gas bubbles fromcontacting and breaking through the surface of the thermoplastic polymer502 as the foamed part is formed. This is achieved by the counteractingpressure being applied by the GCP system 516 into the mold cavity at oraround the same time that the thermoplastic polymer 502 single-phasesolution is injected into the mold cavity 514. The inert gas bubbles aresubjected to forces sufficient to hold the SCF 510 within thethermoplastic polymer 502 during the injection step 610.

Referring to FIG. 6, in steps 612 and 614 the controller 503 manipulatesthe pressure and temperature within the mold 514 to control the physicalfoaming of the thermoplastic polymer 502. Although the steps ofdynamically controlling the temperature of the mold 612 and applying agas counter pressure to the mold 614 are illustrated as separate stepsin the flow chart of FIG. 6, steps 612 and 614 may be conductedsimultaneously or in close succession such that the controller 503temperature and pressure within the mold. In step 612 and 614, nucleigrowth is experienced within the melted thermoplastic polymer 502 and anumber of microcellular bubbles are formed. As the controller 503 (FIG.5) raises and lowers the temperature in step 612, the SCF 510 vaporizesand becomes gas bubbles causing the thermoplastic polymer 502 to foamwithin the mold 514. In step 614 the GCP system 516 sends a pre-metereddose of counter pressure gas into the mold by computer control to createsubstantially uniform bubbles and the gas counter pressure conditionsthe surface texture for an optimal cosmetic appearance. The gas bubblesgrow until the thermoplastic polymer 502 fills the mold 514, and theexpansion capabilities of the SCF 510 are expended. Because the bubblesreach micron sizes, the process produces microcellular foaming. SCF 510concentration may influence the structure of the gas bubbles. Hence, thecontroller 503 selects temperature and gas counter pressure parametersso as to produce a useful and/or determined gas bubble structure. As themolding of the part concludes, the mold cools and the thermoplasticpolymer solidifies. In the embodiment depicted in FIG. 6, in step 616the dynamically temperature controlled mold temperature is switched towater cooling and the formation of the gas bubbles and the expansion ofthe thermoplastic polymer 502 slows and stops. The DMTC 522 quicklycools the mold 514 to a lower limit (the ejection temperature), theflexible foam molded part 402 is now formed and it is ejected from themold.

Recyclable Injection Molded Microcellular Flexible Foam Products

FIG. 4, shows a footwear component of the present disclosure. Morespecifically a recyclable microcellular flexible foam shoe midsole 400that is made of the recyclable flexible foam 402.

As discussed briefly above, the method for manufacturing a recyclablediscussed above augments the environmentally beneficial effects ofutilizing monomers and polymers developed from recycled feedstocksbecause the resulting products may be further recycled into monomersthat can be repolymerized into thermoplastic polymers for use in makingnew other plastic materials. Particularly, producing goods that areconfigured for being recycled ensures that the flexible foam will lastthe usable life of the resulting product, such as by functionalizing itin a manner so that it does not breakdown or fall apart mid-use withinthe finished goods. For example, it would be detrimental for a person topurchase furniture, a pair of shoes, or other athletic equipment thatwere made from the recyclable flexible foam of this disclosure only tohave the foam degrade during regular use before the end of the productsusable life.

More particularly, the present disclosure benefits from the use of aninert physical foaming agent and thermoplastic polymer compoundsenumerated above which are not crosslinked during the manufacturingprocess. The resulting recyclable flexible foams 402 arenon-crosslinked, free from harmful chemical foaming agents such as ADA,and environmentally benign. Furthermore, the recyclable flexible foams402 may be used in numerous types of end-product such as footwear foamsfor use in making shoes.

The recyclable flexible foam 402 may be redirected throughwaste-diversion to an appropriate recycling facility at the end of theproducts useful life. Because the recyclable flexible foam 402 uses nochemical foaming agents such as ADA, and because the method describedherein does not utilize thermoplastic polymers that are crosslinkedduring their manufacture, the recyclable foam 402 may be ground up,pre-processed and depolymerized into one or more monomers. One suchdepolymerized monomer is caprolactam such as ECONYL® caprolactam,whether in flake, liquid or molten, provided by Aquafil USA Inc.,Cartersville, Ga., or depolymerized caprolactam, whether flake, liquidor molten, provided by DSM Engineering Plastics Americas, Troy Mich.

Referring to FIG. 7, the method of the present disclosure contemplates amethod 700 of recycling the recyclable foam 402 utilizing a thermal andchemical depolymerization process according to which the temperature ofa polymer such as PEBA is raised beyond the ceiling temperature, and anyof a number of chemical reagents or catalysts are utilized todepolymerize into its constituent monomers. In the embodimentillustrated in FIG. 7, the depolymerization process begins with step 702mechanically separating the thermoplastic polymer of the recyclable foam402 from any waste. In step 704 a depolymerization catalyst isintroduced to the separated thermoplastic polymer. Non-limiting examplesof depolymerization catalysts include acids such as phosphoric acid andboric acid. In step 706 heat is applied to the such as through asuperheated steam which may act to distil caprolactam and any othervolatile compounds and produces a distillate containing the caprolactammonomer. The temperatures applied may range from about 100° C. to about325° C. In step 708 the distillate is fractionated to separate water andcaprolactam from other byproducts of the depolymerization method. Instep 710, an oxidizing agent is introduced to the separated aqueouscaprolactam. Some non-limiting examples of oxidizing agents includepotassium permanganate, hydrogen, oxygen, potassium dichromate, sodiumor potassium hypochlorites, perchlorites, or perboric acid. In step 712the oxidized aqueous caprolactam is concentrated such as throughevaporation. In step 714 the concentrated caprolactam monomer ispurified such as through vacuum distillation.

After purification of the caprolactam monomer in step 714, thedepolymerized monomers may be repolymerized into thermoplastic polymersand utilized to make more recyclable flexible foam 402. Thus, the methodof the present disclosure establishes a circular process wherebymanufactured products can be broken down, manufactured into newproducts, and reinserted into the stream of commerce, as opposed tousing new raw fossil fuels or other non-renewable feedstocks. Moreover,recyclable foams 402 of the present disclosure do not compromise oneither technical performance properties during their useable life, noron their environmentally conscious design.

As discussed herein above, the devices, systems, and their methods ofuse may be employed for the purpose of producing one or more molded endproducts, such as for components for use in footwear, seating,automotive, protective gear, and/or sports gear. Accordingly, in variousembodiments, provided herein is one or more components useful in theconstruction of a shoe, such as a sole, midsole, and/or insole thereof,such as where the sole forms the base of the shoe, and is configured formaking contact with the ground, the midsole forms an intermediatestructural and cushioning element, and the insole is configured forbeing inserted within a shoe and thereby providing cushioning and/orsupport to the shoe.

In certain embodiments, the shoe component may include a recyclable foam402 produced according to the method 600 disclosed herein that may beenvironmentally friendly and recyclable. In various instances, eachindividual component may be composed of a plurality of layers includinga base layer and a cushioning layer. For instance, in particularembodiments, a support member such as a support member being coupled tothe base layer may be included, and where the component is an insole,having one or more of an arch contacting or heel contacting portion.

Particularly, in various embodiments, a foamed material may be producedsuch as where the foam materials may be used in the production ofcushions, cushioned furniture, shoe components, such as insoles thereof,mats, fibers, weaves, and the like. Other useful products may includecaulking, such as silicone caulking, silicone medical gloves, siliconetubing for drug delivery systems, silicone adhesives, siliconelubricants, silicone paints, and other suitable silicone products, e.g.,condoms. In various embodiments, the foam products may be produced in amanner where the foamed material may have one or more anti-microbial,anti-bacterial, anti-fungal, anti-viral, and/or anti-flammableproperties.

More particularly, in one aspect, this disclosure may be directedgenerally to a process for the manufacture of furniture, such asupholstered furniture and/or the cushions thereof, such as furniturethat includes or is otherwise comprised of foam, e.g., that isbiodegradable and/or compostable. Hence, the recycled foams of thedisclosure are advantageous for use in the manufacture of furniture thatincludes such produced foam inserts. The recyclable foam producedaccording to the method of the present disclosure have proven to beadvantageous for use as cushioning materials, such as for pillows,couches, beds, seat cushions, or for other upholstering furniture, andthe like.

For instance, the method 600 may be used to produce a small to largeblock of recyclable foam 402, such as to form a foam insert for use infurniture or car accessory components. The block foam may then be cutinto smaller blocks of the desired size and shape, based on the type andform of the furniture being produced. Specifically, the sized and cutblocks may then be applied to or otherwise fit within the furniture orcar frame or other bounding material, together which may be covered toproduce the final furniture product, whether it be a pillow, sofa, acushion, e.g., a sofa or car cushion, or the like. Additionally, wheredesired, an outer casing or bounding material may be attached to theframe material, such as by stapling, and/or tacking, or otherwisefastened to the frame of an article to be upholstered and covered with afabric or other material.

Accordingly, in various embodiments, manufacturing upholsteredfurniture, such as a couch or a car seat, a frame may be produced.Various internal, e.g., structural, components of the furniture may beinstalled within the frame, such as springs or the like, and then thesheets of the recyclable flexible foam 402 may be positioned in, over,and around the springs, such as for cushioning and/or insulation. Ofcourse, other materials may be included, such as layers of cotton, wool,felt, rubber-based products, and the like, and a cover material may thenbe added so as to cover the frame and finish the product manufacture.

Specifically, the recyclable foams of the present disclosure along withother materials disclosed herein may function as padding, or filling,which may be shaped, adjusted, and tucked beneath a cover as the covermaterial is stretched over the frame. Additionally, as indicated, invarious instances, the recyclable foam produced herein is useful in andabove those known in the art for a number of reasons, not the least ofwhich is the fact that typical PU and/or EVA foams are not recyclable,whereas the component of the foams produced herein are. Hence, invarious embodiments, a method of constructing furniture upon an openframe is provided.

Further, in another aspect, this disclosure is directed generally to aprocess for the manufacture of shoe components, such as soles, midsoles,and/or the insoles of shoes, such as shoe components that include or areotherwise comprised of conventional foam. Specifically, in particularembodiments, methods for making recyclable soles, midsoles, insoles,and/or other shoe inserts are provided. For instance, the present shoeinsert may be a form of cushioning device that is adapted to be insertedor otherwise fit within a shoe, e.g., a running shoe or sneaker, whichmay be configured so as to reduce the impact of a foot hitting asurface, e.g., the ground while running or walking, thereby absorbingand/or attenuating shock to the foot.

Particularly, shoe sole components, including midsoles and inserts mayinclude one or a multiplicity of layers. For instance, in someinstances, a base layer, a recyclable foam layer, and/or a fabric layermay be provided. Specifically, a base layer of a relatively resilientmaterial, and/or a recyclable foam layer disposed over the base layer,and/or a fabric layer disposed over the recyclable foam layer may beincluded. Accordingly, the method may include integrally forming thebase layer, the recyclable foam layer, and the fabric into atri-laminate sheet. In various instances, a support layer may bedisposed at a heel area, which support layer may be constructed of arigid material, such as of higher density than that of the othercomponents of the laminate. An adhesive, glue, or other attachmentmechanism may be provided and employed for attaching and forming thetri-laminate with the support layer.

More particularly, in other instances, the method for making a shoecomponent, such as an insole, may include the steps of: providing arecyclable foam layer, providing a fabric layer, heating the recyclablefoam layer, joining the recyclable foam and fabric layers; providing abase layer, e.g., a base layer having a density that is the same,greater, or a lesser density as that of the recyclable foam layer; andheating at least one of the base layer and foam layer so as to couplethe base layer with the recyclable foam layer so as to form a dual ortrilaminate.

The methods may further include providing a pre-formed support member,such as an arch support and/or heel member, which members may have adensity substantially the same, or less, or greater than the density ofthe foam layer. In particular instances, the support member may beformed of a compressed foam material so as to obtain greater density,and thus greater rigidity in comparison to that of the recyclable foamlayer. Additionally, a heat and/or pressure reactivatable adhesive maybe applied between the support and/or heel member and the laminate. Amolding pressure may then be applied to the composition so as to causethe forming and/or shaping of the trilaminate into the support and/orheel member so as to form an integral one-piece shoe insert, with thepre-formed heel member forming a rear portion and/or the support memberforming a mid-portion of the bottom surface of the finished shoe insert,e.g., at the mid and/or heel area thereof, and the base layer formingthe bottom surface of the finished shoe insert at the forward areathereof.

It is to be noted, however, that a support and/or heel member need notbe included, and in some instances, one or more of the laminatecomponents may be excluded or other laminate layers added. It is furtherto be noted that, in certain embodiments, the recyclable foam layer maybe more flexible and/or cushioning, e.g., having a greater durometer,than the base layer, which in turn may be more flexible and/orcushioning, e.g., having a greater durometer, than the support member.Hence, the more flexible foam and base layers may be relativelyresilient and conform in shape to the desired shoe size andconfiguration, whereas the support layer(s) may be relatively morerigid.

Specifically, the support layer may be of a denser recyclable foam thusmaking the support layer more rigid. Hence, in various embodiments, therecyclable foam layer may have a density of about 2 or about 3 or about5 to about 10 lbs. per cubic ft. or more, such as a density in the rangeof between about 4-6 lbs. per cubic ft. Additionally, the recyclablefoam layer may have thickness of approximately ⅛″, such as in a range ofthickness of about 3/32″- 5/32″.

Likewise, the base layer may also have a density of about 2 or about 3or about 5 to about 10 lbs. per cubic ft. or more, such as a density inthe range of between about 4-6 lbs. per cubic ft. The thickness of thebase layer may be on the order of about 5/16″+ or −10%. However, invarious instances, the thickness of the base layer may range from about¼″ or less to about 7/16″ in thickness. With regard to the supportlayer, which may be formed primarily at the arch and/or heel areas ofthe insert, which may also be made of the recyclable foam disclosedherein.

However, the support layer may be made by compressing recyclable foam402 so that the final density is on the order of 22-23 lbs. per cubicft. The fabric layer may be constructed of any suitable material, forexample, cotton, polyester, or a polypropylene knit. In variousinstances, the material and recyclable foam layers may be laminatedtogether by a flame lamination technique that employs an open flamewhich generates sufficient heat to cause the surface of recyclable foamlayer to melt. Once melted, the fabric layer is joined to the recycledfoam layer and chilled rollers so that the two layers are joinedtogether.

At this point in the process, these layers are still maintained in aflat sheet form. These integrated layers may then next joined, also byflame lamination, to the base layer. The previously integrated materialand foam layers may be joined to the support layer and thesemulti-laminated layers may then be run between chilled rollers. At thisstage of the process, these layers are still in flat sheet form. Thelayers thus laminated to this point are then ready for molding. This maybe performed by heating the laminated layers to a molding temperature ofapproximately 250 F, such as for a period of about 1 to about 5 minutesor more, e.g., about 225 seconds. This heats the previously laminatedlayers sufficiently to permit them to be inserted into a mold.

As mentioned above, the SCF physical foaming agent may be selecteddependent upon the desired characteristics of the end product. Carbondioxide, which becomes an SCF fluid at 31.1 Celsius and 72.2 bar, is 4to 5 times more soluble in thermoplastic polymers 502 than nitrogen,which becomes a supercritical fluid at −147 Celsius and 34 bar. Thesaturation point in an unfilled recyclable thermoplastic polymer isabout 1.5 to 2 percent by weight of nitrogen, depending on temperatureand pressure conditions, while the saturation level of carbon dioxide iscloser to 8 percent by weight. Carbon dioxide also exhibits a greatermobility in the biopolymer, allowing it to migrate further into existingbubbles than nitrogen. From the perspective of cell nucleation, greatersolubility and mobility means fewer cells will be nucleated, and thosethat do nucleate will tend to be larger.

In the embodiments discussed above, where the method 600 is used toproduce athletic goods such as shoes, the SCF 510 comprises nitrogen ina critical state. Nitrogen provides improved weight reduction and finenuclei at much lower weight percentages than SCF carbon dioxide. SCF 510nitrogen levels are at least 75 percent lower than the SCF carbondioxide level required to achieve comparable parts. So being, thegreatly reduced SCF nitrogen level requirements when compared to SCFcarbon dioxide ensures the optimal material savings and time savingswhen mass producing the biodegradable and industrially compostableflexible foams of the present disclosure as employed in making shoecomponents.

While carbon dioxide is heavier it may be a suitable foaming agent incertain applications, such as when viscosity reduction is a goal of theprocess, and/or when the end product can't tolerate SCF nitrogen's moreaggressive foaming action, or in semi-flexible foams. For example, whenthe method 600 is used to produce furniture and automotive products, theSCF 510 comprises carbon dioxide in a critical state because carbondioxide produces a much larger cell structure, albeit at greater sizeand/or weight. During the physical foaming process with a physicalblowing agent, a depression in the glass transition is seen.

As discussed briefly above, carbon dioxide in a super critical state maybe utilized as the physical foaming agent when the amount of nitrogenneeded to produce a part is so low that it is not possible toconsistently process parts. Since carbon dioxide is a less aggressivefoaming agent, in some applications it is easier to run low levels ofcarbon dioxide. For example, 0.15 or 0.2 percent carbon dioxide (ascompared to levels of nitrogen at less than 0.05 percent) may beutilized to produce soft materials and parts having thick crosssections.

Although a few embodiments have been described in detail above, othermodifications are possible. Other embodiments may be within the scope ofthe following claims.

1. A method for manufacturing a recyclable flexible foam molded productcomprising: providing a thermoplastic polymer precursor comprising atleast one monomer derived from depolymerized post-consumer plastic;inserting a fluid into a barrel of a molding apparatus under temperatureand pressure conditions to produce a super critical fluid; mixing thethermoplastic polymer precursor and the super critical fluid to create asingle phase solution; injecting the single phase solution into a moldof an injection molding machine wherein the mold is under gas counterpressure; and foaming the SCF-impregnated single phase solution bycontrolling heat and temperature conditions within the mold.
 2. Themethod in accordance with claim 1, wherein the thermoplastic polymerprecursor comprises at least 40% of the monomer derived fromdepolymerized post-consumer plastic.
 3. The method in accordance withclaim 2, wherein the thermoplastic polymer precursor comprises at least60% of the monomer derived from depolymerized post-consumer plastic. 4.The method in accordance with claim 3, wherein the thermoplastic polymerprecursor comprises 90% or more of the monomer derived fromdepolymerized post-consumer plastic.
 5. The method in accordance withclaim 1, wherein the monomer comprises caprolactam.
 6. The method inaccordance with claim 1, wherein the thermoplastic polymer precursorcomprises a polyamide based thermoplastic elastomer.
 7. The method inaccordance with claim 6, wherein the thermoplastic polymer precursorcomprises a copolymer including at least one caprolactam monomer.
 8. Themethod in accordance with claim 1, further including the step ofrecycling a flexible foam by depolymerizing the flexible foam into oneor more monomers.
 9. The method in accordance with claim 8, wherein theflexible foam is depolymerized into caprolactam.